Citation
Evaluation of the sticking potential of clays to a tunnel boring machine cutterhead

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Title:
Evaluation of the sticking potential of clays to a tunnel boring machine cutterhead
Creator:
Tokarz, Sean ( author )
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
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English
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1 electronic file (182 pages) : ;

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Subjects / Keywords:
Clay soils ( lcsh )
Swelling soils ( lcsh )
Tunneling ( lcsh )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Review:
In recent years there has been a trend in the tunneling industry towards underground projects within increasingly complex geologic settings. Advancing a TBM through a potentially adhering or "sticky" clay formation may present issues for the construction schedule and therefore budget. Several factors influence the potential for a clay to adhere to the excavating face of a TBM. The factor that most contributes to clay sticking potential is the swelling capacity which is most commonly estimated from the Atterberg limits of the clay. The other important factors is the moisture content of the sample which, assuming the formation is below the groundwater table, typically depends on the consolidation state and overburden history of the clay. Some other important considerations include the material type and surficial microroughness of the excavation face and tooling of the TBM. Historical studies which included interfacial testing provide a lot of information on the mechanism and representative constitutive models for the interfacial shear strength between soil and construction grade steel materials. More recent studies have focused specifically on the application to soft ground tunneling. Multiple adhesion tests including this study and ones performed previously indicate that thresholds for sticking potential include a surficial roughness of greater than 2um for stainless steel surfaces and a clay plasticity index greater than 20 with a consistency index between 0.3 and 0.7. An independent testing program utilizing a ring shear device with modified top and bottom rings in presented in detail. Results indicate good repeatability and compare well with previous adhesion tests using modified direct shear apparatus. The relative benefit of the ring shear device over the direct shear device is the more uniform distribution of shear strains and the ability to test a clay to residual strengths without stopping to reverse shear direction. The drawback is the time and attention to detail required to mold the4 sample into the cylindrical chamber. Results from 10 ring shear adhesion tests indicate that maximum previous confining pressure has a significant effect on adhesive strength and a bi-linear Mohr Columb type strength is representative model for the interfacial shear strength.
Thesis:
Thesis (M.S.)--University of Colroado Denver. Civil engineering
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Includes bibliographic references.
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System requirements: Adobe Reader.
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Department of Civil Engineering
Statement of Responsibility:
by Sean Tokarz.

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University of Colorado Denver
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|Auraria Library
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900223319 ( OCLC )
ocn900223319

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EVALUATION OF THE STICKING POTENTIAL OF CLAYS TO A TUNNEL BORING MACHINE CUTTERHEAD by SEAN TOKARZ B.S., Colorado School of Mines, 2007 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Masters of Science Civil Engineering 2014

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ii This thesis for the Master of Science degree by Sean Tokarz has been approved for the Civil Engineering Program by Nien Chang, Chair Aziz Kahn Brian Brady May 2nd, 2014

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iii Tokarz, Sean (M.S., Civil Engineering) Evaluation of the Sticking Potential of Cl ays to a Tunnel Boring Machine Cutterhead Thesis Directed by Professor Nien Chang ABSTRACT In recent years there has been a trend in the tunneling industry towards underground projects within increasingly complex geol ogic settings. Advancing a TBM through a potentially adhering or sticky clay formation may present issues for the construction schedule and therefore budget. Several factors in fluence the potential for a clay to adhere to the excavating face of a TBM. The factor that most contributes to clay sticking potential is the swelling capacity which is most commonly estimated from the Atterberg limits of the clay. The other important factors is the moisture content of the sample which, assuming the formation is below the groundwater table, typic ally depends on the consolidation state and overburden history of the clay. Some other im portant considerations include the material type and surficial micro-roug hness of the excavation face and tooling of the TBM. Historical studies which include interfacial testing provide a lot of information on the mechanisms and representative constitutive mode ls for the interfacial shear strength between soil and construction grade steel materials. Mo re recent studies have focused specifically on the applications to soft ground tunneling. Mu ltiple adhesion tests including this study and ones performed previously indicate that thresholds for sticking potential include a surficial roughness of greater than 2m for stainless steel surfaces and a clay plasticity index greater than 20 with a consistency index between 0.3 and 0.7.

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iv An independent testing program utilizing a ring shear device with modified top and bottom rings is presented in detail. Results indica te good repeatability and compare well with previous adhesion tests using modified direct sh ear apparatus. The relative benefit of the ring shear device over the direct shear device is the more uniform distribution of shear strains and the ability to test a clay to residual strengths without stopping to reverse shear direction. The drawback is the time and attenti on to detail required to mold the sample into the cylindrical chamber. Results from 19 ri ng shear adhesion tests indicate that maximum previous confining pressure has a significant effect on adhesive strength and a bi-linear Mohr Columb type strength is a representative model for the interfacial shear strength. The form and content of this abstract ar e approved. I recommend its publication. Approved: Nien Chang

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v ACKNOWLEDGEMENTS I would like to thank my advisor for pushing me to create this original work, my family for teaching me to never quit on the th ings that matter and most of all Jamie, for keeping me going.

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vi TABLE OF CONTENTS Chapter 1Introduction .................................................................................................................. ........................... 11.1Sticky Clays in TBM Drives .................................................................................................... ..... 11.2Research Objectives ........................................................................................................... ........... 21.3Testing Program ............................................................................................................... ............. 31.4Organization of Report ........................................................................................................ ........ 32Literature Review ............................................................................................................. ....................... 62.1Soft Ground Tunneling with TBMs ........................................................................................... 62.1.1Types of TBMs ................................................................................................................. 62.1.2Forces on TBM Cutter Head .......................................................................................... 92.1.3Clogging of TBMs .......................................................................................................... 112.2Clay Mineralogy ............................................................................................................... ............ 122.2.1Formation and Composition of Clays ......................................................................... 122.2.2Surface Area and Activity of Clay Minerals ................................................................ 132.3Mechanical Properties of Clays ...................... .......................................................................... 162.3.1Atterberg Limits .............................................................................................................. 162.3.2Shear Strength of Clays .................................................................................................. 162.3.3Adhesive Strength of Clays ........................................................................................... 172.3.4Consistency of Clays & the Effects of Stress History ............................................... 203Previous Studies .............................................................................................................. ...................... 233.1Historical Studies ............................................................................................................ ............. 233.2Recent Studies................................................................................................................. ............. 30

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vii 3.3On-Going Research ............................................................................................................. ....... 404Industry Experience and Case Studies ................. ......................................................................... ..... 445Description of Testing Program ......................... ....................................................................... ......... 515.1Previous Laboratory Testing Programs ................................................................................... 515.2Clay Sample ................................................................................................................... ............... 525.3Consolidation Testing ......................................................................................................... ....... 545.4Bromhead Ring Shear Apparatus ............................................................................................. 555.5Modified Ring Shear Interface Test ......................................................................................... 565.5.1Modified Ring shear Assembly Procedures: ............................................................... 605.5.2Sample Preparation Procedures: ................................................................................... 605.5.3Interface Ring Shear Testing Procedures: ................................................................... 636Results of Testing Program .................................................................................................... ............. 676.1Atterberg Limits .............................................................................................................. ............ 676.21-D Consolidation Testing ..................................................................................................... ... 686.3Modified Ring Shear (Adhesion) Test ...................................................................................... 726.3.1Interface Shear Test ....................................................................................................... 756.3.2Effect of Ring Surface Roughness ............................................................................... 786.3.3Effect of Over Consolidation ....................................................................................... 806.3.4Consolidation During Shear Testing ........................................................................... 826.3.5Interface Shear Strength ................................................................................................ 866.3.6Moisture Content Measurements ................................................................................. 907Summary and Conclusions ....................................................................................................... ........... 927.1Ring Shear Device Interface Testing ........................................................................................ 947.2Comparison of Results from Previous Studies ....................................................................... 98

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viii 7.3Implications for TBM Cutter head & Excavation .............................................................. 1068Recommendations ............................................................................................................... ............... 109References .................................................................................................................... ................................... 111 Appendix A B C D E Manual For The Bromhead Ring Shear Apparatus Specifications For Modified Steel Testing Rings 1-D Consolidation Test, Laboratory Observations Normally Consolidated Ring Shear Adhesion Test, Laboratory Observations Overly Consolidated Ring Shear Adhesion Test, Laboratory Observations

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ix LIST OF TABLES T able 1 Comparison of typical Clay Propertie s Atterberg Limits, Acitivity and Cation Exchange Capacity ............................................................................................................. .............. 152 Results of Consolidated Undrained and Drained Direct Shear Box Tests & Steel Interface Shear Tests ......................................................................................................... ............... 253 Cone Pull Out Test Results Tensile Strength Vs. Displacement for a cone inclination of 58 degrees and an overconsolidated clay .............................................................. 424 Properties of Kaolin Clay (Old Hickory Clay Company) ........................................................ 535 Summary of Atterberg Limit Tests ......................................................................................... ..... 676 Summary of Results from 1-D Consolidation Tests ................................................................. 707 Summary of Results of Normally Conso lidated Ring Shear Interface Tests for Top Ring = 2m .................................................................................................................... ................... 768 Summary of Results of Normally Conso lidated Ring Shear Interface Tests for Top Ring = 20m ................................................................................................................... .................. 779 Summary of Results for Overly Consolidated Ring Shear Tests ............................................ 8010 Interface Shear Strength between Ka olin and Top Steel Ring with Roughness = 2m 8711 Interface Shear Strength between Ka olin and Top Steel Ring with Roughness = 20m .......................................................................................................................... ......................... 8712 Moisture Contents Before and After Norm ally Consolidated Shear Testing ....................... 9113 Moisture Contents Before and After Over ly Consolidated Shear Testing ............................ 9114 Consistency Index of Clay Samples Tested ....... ......................................................................... 95

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x LIST OF FIGURES Figure 1 Earth Pressure Balance Machines with Face Support Provided by Mechanical Means with Compressed Air (Left) and Pressureized Bentonite Slurry (Right). (From International Tunneling Association Mechanized Tunneling Working Group, 2000) ......................................................................................................................... ............................ 82 Primary Forces Acting on a TBM Cutter Head in Soil ............................................................ 103 Photographs Taken from Recent Projects Showing buildup of Clays in The Working Chamber (left) and on the Cutter Head (r ight) of a TBM. ........................................ 124 Stacking of clay molecules (from Das, 2008) ............................................................................. 135 Surface activity of common clay minerals (from Lamb & Whitman, 1969) ......................... 146 Adhesion Model (from Zimnik, 2000) ....................................................................................... 197 Theoretical shape of adhesive shear strength envelope based on clay microstructure and real contact area (from Kooistra, 98) .......................................................... 228 Modified Lower Half of Shear Box for Adhesion Testing (from Littleton, 1976) .............. 249 Stress Displacement Curves for Un drained Shear Box Tests on Normally Consolidated Sample 1 (from Littleton, 1976) ............................................................................. 2610 Stress Displacement Curves for Undr ained Shear Box Tests on Overconsolidated Sample 2 (from Littleton, 1976) ............................................................................................... ...... 2711 Rmax measurements for different prepar ed steel surfaces (left). Photo of Prepared Interface Ring Shear Surface for Rmax = 220 m (0.22mm) (from Yoshimi, 1981) .............. 2912 Test Results for Ring Shear Interface Testing Between Steel and Tonegawa Sand for Confining Pressure = 105kPa (from Yoshimi, 1981) ........................................................... 2913 Coefficent of Friction between Different Sands and Prepared Steel Surface for Confining Pressure = 105kPa (from Yoshimi, 1981) .. ................................................................ 3014 Schematic of Testing Apparatus used by Thewes to Evaluate sticking potential of clays (Thewes, 2005) .......................................................................................................... ............... 3115 Evaluation of the Clogging Potenti al for Clays in Slurry Faced TBM Drives (Thewes, 2005) ................................................................................................................ .................. 3316 Influence of Roughness in Direct Shea r Adhesion Tests with Contact Time of 1Hour (Zimnik, 2000) ........................................................................................................... ............. 36

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xi 17 Influence of Contact Time in Direct Shear Adhesion Tests, Steel plate with roughness of 0.2 m (Zimnik, 2000) .............................................................................................. 3718 Results of Modified Shear Box Tests (from Kooistra 1998) ................................................... 3919 Cone Pull Out Testing Apparatus, de veloped by InProTunnel Working Group (from Feinendegen et al, 2010) ................................................................................................ ....... 4120 Proposed adherence Classification System based on the Cpone Pull Out Test (from Spagnoli, 2010) ......................................................................................................... .............. 4321 Clogging Risk of Thessaloniki M etro based on the Thewes method (from Marinos, 2007) ......................................................................................................................... .......................... 4522 Potential for Sticky Behavior of Cohe sive Soils of Thessaloniki Metro based on the Geodata-Torino method (from Marinos, 2007) .................................................................... 4523 Independent Cutter Head Used in TBM on Subway Essen Lot 34 Project (from Waays, 1995) .................................................................................................................. .................... 4724 Photograph of 1-Dimensional Wykham Fe rrace Consolidometer ......................................... 5425 Photographs of Wykham Ferrace Ring Shear Apparatus ........................................................ 5526 Schematic of Top Steel Rings ............................................................................................ .......... 5827 Photographs of Top Stainless Steel Rings ................................................................................ .. 5928 Results of 1-D Consolidation Test for Confin ing Pressure = 0.25tsf ................................... 6829 Results of 1-D Consolidation Test for Confin ing Pressure = 0.5tsf ...................................... 6930 Results of 1-D Consolidation Test for Confin ing Pressure = 1.0tsf ...................................... 6931 Results of 1-D Consolidation Test for Confin ing Pressure = 0.25tsf ................................... 7032 Interpretation of Results from 1-D Consolidat ion Tests ......................................................... 7133 Screenshot of Proving Ring Displacemen t Gage from Video Recording Device ............... 7234 Results of Normally Consolidated Ring Shear Interface Tests for Top Ring = 2m ......... 7635 Results of Normally Consolidated Ring Shear Interface Tests for Top Ring = 20m .......................................................................................................................... ......................... 7736 Comparison of Results of Normally Consolidated Ring Shear Interface Tests for Top Ring = 2 m & 20m ........................................................................................................ ...... 7937 Results of Overly Consolidated Tests .......... .......................................................................... ..... 8238 Consolidation of Samples during Ring Shea r for Top Ring = 2m ....................................... 8339 Consolidation of Samples during Ring Shear for Top Ring = 20m ..................................... 8340 Vertical Displacement of Overly Consolidated Samples ......................................................... 84

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xii 41 Normal Vs. Shear Stress Test Results for Top Ring Roughness = 2m ............................... 8642 Normal Vs. Shear Stress Test Results for Top Ring Roughness = 20m ............................. 8743 Normal Vs. Shear Stress Test Results, Peak St rengths ............................................................. 8844 Normal Vs. Shear Stress Test Results, Residu al Strengths ...................................................... 8845 Location of Overly Consolidated Peak Strength Tests Relative to Normally Consolidated Strength Envelope for Top Ring Roughness = 20m........................................ 8946 Location of Overly Consolidated Residu al Strength Tests Relative to Normally Consolidated Strength Envelope for Top Ring Roughness = 20m........................................ 9047 Comparison of Clay Samples from Various Studies ................................................................. 9948 Comparison of Test Results for Con solidated Drained Modified Direct Shear Tests Conducted by Littleton .................................................................................................. .... 10149 Summary of Results from Various Au thors for Consolidated Drained Modified Direct Shear Tests ............................................................................................................ ............. 103

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1 1 Introduction 1.1 Sticky Clays in TBM Drives The tunnel boring machine (TBM) is increasingly the method preferred by contractors and owners to construct linear underground excavations (tunnels) in soil and soft sedimentary rocks. With this trend and the ever evolvi ng technology comes increased efficiency which positively impacts construction schedule and cost increased effectiveness at preventing third party impacts, and increased safety for underg round workers who are no longer exposed to an excavation face without control measures. While the efficiency gained from a properly designed and operated TBM can provide a monu mental benefit to project execution, a TBM which is not designed to suit or not properly operated for the particular ground conditions can prove devastating to the project delivery and have negative implications for workers and nearby residents. The issues associated with reduced progre ss rates and temporary work stoppages at a construction site are compounded in the case of tunneling. For most underground projects the tunnel excavation is the only construction acti vity that can take place following initiation of the TBM advance and installation of the final facilities cannot begin until it is complete. In other words the excavation face is always the critical path and if advancement is hindered or halted, so follows construction progress. This rule of the underground industry in combination with the increasingly comple xity of the tunnel boring machines and the geological settings which are being attempted with underground methods leads to a greater need for the geologist, geotechnical engineer TBM designer and manufacturer, contractor and client to have awareness of the potential i ssues. Additionally, since a single excavation is typically performed with the use of only one machine, complex or changing geologic

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2 conditions dictate the need for a jack of many trades TBM capable of overcoming multiple obstacles which may be in no way related to one another. One such obstacle that has received increased attention in recent years is the effect of sticky or clogging clays on TBM excavati on progress. Reduced advancement rates in large projects in Europe and the US in addi tion to the clogging of ill equipped TBMs on several smaller projects has created a need for increased understanding of the phenomena and potential mitigation techniques. Early id entification in a project life-cycle and the opportunity for avoidance of problematic geolog ic environments may be as important as these reactionary mitigation techniques. 1.2 Research Objectives The purpose of this study is to identify the contributing factors in the adherence of clays to excavation equipment, with a focus on the cu tterhead and working chamber of a TBM. Secondly, to provide a summary of the most important research to date on the subject and the state of the art for the identification of st icking clay potential for a TBM drive. Several case studies have also been summarized to show how the current research relates to industry practice. A testing program, utilizing the ring or torsion shear apparatus will be conducted to provide some independent test results to compare with the results from previous adhesion studies. The pros and cons of the use of the ri ng shear device in adhesion studies will also be discussed. Finally, the results from previous stud ies and this new information will be used to draw conclusions on the important geological and mechanical factors to TBM clogging and compare with the current practice. Recommend ations based on these findings will be provided at the end of this report.

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3 1.3 Testing Program The proposed independent testing program includ es testing of a Kaolin Boom clay sample with a moderate sticking potential using the simple ring torsion device. The sample was chosen because it exhibits properties not un common in nature and in underground projects. The benefits of using the ring shear device will be discussed in detail and includes a relatively consistent distribution of strains across a samp le and the ability to test a shear surface over a (theoretically) infinite length of displacement, which is similar to the rotation of a TBM cutter head. Two different rings with very diffe rent roughness coefficients similar to those found on TBM excavation tools will be used for the clay-steel interface shear testing. Additionally measurements for moisture c ontent (consistency), atterberg limits and consolidation parameters will be conducted to compare with shear testing results and other studies. 1.4 Organization of Report The report is organized into the following broad based sections with the following objectives: 1.0 Introduction State the subject problem and need for further study, state the objective of the research project, summarized the proposed testing program and how it relates to the subject matter. 2.0 Literature Review Provide a summary of the contributing factors to TBM clogging from the industry guidelines, disc uss the types and implications of

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4 different clay mineralogy and prov ide a summary on their effects to the mechanical properties of clays in the field. 3.0 Previous Adhesion Studies Provide a summary of historical, recent and on-going research into the phenomena of clay adherence to steel construction materials. For the purposes of this re port historical will refer to older studies focused on interface testing and recent studies focused specifically on clays adhering to TBM machinery. The summary for each will focused on factors and resul ts that pertain to the proposed independent testing program and its results and conclusions. 4.0 Industry Experience & Case Studies Prov ide a brief summary of notable projects from around the world that encountered sticky clays in either the investigation or construction phase or both. Discuss how the issue was identified and/or mitigated both before and during construction. 5.0 Description of Testing Program Presen t the proposed testing program and how the intended methods meet the stated goals of this study. Provide information on the clay sample and the specially prepared ring materials used for testing. Provide details on applicable standards, sample preparation, testing proced ures and data acquisition methods. 6.0 Results of Testing Program Present the re sults of the testing program in terms of the testing program outlined in Section 5. Explain how the consolidation and atterberg limit tests provide the parameters needed to conduct the modified ring shear tests. Describe the results of the interface testing in detail and provide a summary of the measured interface strength envelopes and points.

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5 7.0 Summary & Conclusions Summarize previous testing and compare with geomechanical mechanisms for clay interface shear strength. Summarize and discuss the observations from the testing program and how the results and interpretations apply to the soft ground tunneling practice. Cross compare results with previous and current research studies. Draw conclusions based on the comparisons 8.0 Recommendations Provide recommendations for the tunnel boring machine industry practice and for future studies.

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6 2 Literature Review 2.1 Soft Ground Tunneling with TBMs The use of Tunnel Boring Machines (TBMs) has been gaining acceptance as the preferred method for constructing linear underground st ructures over the last 40 to 50 years. TBMs are commonly used for excavating tunnels for use in transportation, water conveyance including sewer, distribution and hydropower applications and installation of utilities particularly in highly populated urban envir onments. The benefits of using a tunnel boring machine to excavate in soft ground situations include safety, efficiency and effectiveness of the final product. Today it is common to use a tunnel boring machine in all soft ground tunneling projects except where the drive length is too short to justify the upfront cost of a machine or where the geometry of the tunnel is too complicated. 2.1.1 Types of TBMs It is important to understand the different typ es of TBMs used in soft ground environments and the criteria used to choose one type of TB M over another. The basic types of soft ground TBMs available include Shielded TBMs including open spoke type or closed shields plate type, compressed air machines, Earth Pressure Balance Machines (EPBMs) and slurry face machines. Open face shielded machines or spoke cutterheads are most common in excavations in hard rock and are typically only used for soft ground applications in stable, overconsolidated and thus dry clayey soils (I TA, 2000). For closed face shielded machines mechanical support is provided to the excava tion face by an almost closed cutterhead consisting of plates located between the spokes which contain the cutting tools. Slits between the spokes allow the excavated material to pass through the excavation chamber into the working chamber. Closed face shielded machines are typically used in stable or non-

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7 stable cohesive of mixed fine and coarse grai ned cohesive soils with cohesion values ranging from 5 to 30 kN/m (ITA, 2000). By modifying either the open or closed face TBMs or the tunnel itself to include an air tight bulkhead compressed air can be applied to the excavation face for using these machines below the groundwater table. Although this technique is not as common today as the availability of EPBM and slurry machines had become more widespread. Earth Pressure Balance machines (EPBMs) converts the excavated material from the cutting face into a high density slurry mix located in the working chamber whic h is closed off from the remainder of the machine by a steel bulkhead. A specially designed extraction conveyor screw maintains pressure in the working chamber while extracting the excavated material at a controlled rate in order to maintain adequa te face support. In order to maintain the appropriate consistency of th e face support mixture the exca vated soil must contain a significant proportion of fine grained material an d groundwater has to be present. In some instances additives and additional water are adde d into the working chamber to maintain the consistency of the face support medium. Slurry faced TBMs are a particular type of EPBMs in which a fluid is used to support the excavation face. The slurry is pumped into the working chamber under pressure and the slurry-spoil mix is pumped away from the fa ce for separation and recycling. In order to maintain face stability the density and viscosity of the fluid must be controlled at all times. Typically bentonite and foam polym ers are added to the slurry for this purpose. Slurry type EPBMs are commonly used in non-cohesive soils above or below the groundwater table and can be used in locations with high groundwater pressures such as for a lake tap. It is typically

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8 preferable that the soils have a fine grained fr action of 10% or less, otherwise the excavated spoils is difficult to separate from the slurry. Generalized schematics of the EPBM and slurry face type machines are shown in Figure 1 Figure 1 Earth Pressure Balance Mach ines with Face Support Provided by Mechanical Means with Compressed Air (Left) and Pressureized Bentonite Slurry (Right). (From International Tunneling Association Mechanized Tunneling Working Group, 2000) The cutterhead of a TBM can be designed to include several different types of cutting tools or bits. Some of these bits include teeth bits peripheral bits, center bits, gouging bits and wearing bits. Bits are generally made of steel or hard chip alloy which can be several times more durable than steel and therefore more resistant to wear. Selection of the bit type, shape and size is typically based on the geologic c onditions, penetration depth, excavation speed and the length of the drive. The wear on th e cutting tools during construction can be estimated using the following formula (ITA, 2000):

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9 Where: d = amount of wear (mm) K = Wear coefficient (mm/km) D = Distance between center of cutterhead and bit location (m) N = Revolutions of the cutterhead per minute (rpm) L = Excavation Distance (m) The wear coefficient is typically given by the manufacturer and is based on the pressure applied to the tool against the face, the geological conditions, bit material, rate of advance and rotational speed. The design cutter head rotational speed is inversely proportional to the cutter head diameter to limit the velocity of the peripheral cutters. The amount of torque required to rotate the cutter head is dependent on the amount of thrust applied at the face. High contact pressures caused by high torque ma y slow or stop (stall) a machines progress. 2.1.2 Forces on TBM Cutter Head The act of excavating a geologic formation wi th the use of a TBM creates active forces caused by the construction activities and passive or reactive forces in the surrounding soil and in its pore water. Active forces include (Festa, 2012): Contact Pressure between the cutting wheel and the soil; Hydrostatic pressure exerted by face support fluid; Weight of the cutting wheel, TBM shield su pport fluid, and lining (typically steel or concrete); Longitudinal component of advance force from thrust cylinder; Pulling force due to trailing gear; Torque of the cutting wheel created by the cutter motor.

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10 There is a slight moment arises due to the we ight of the wheel which for practical purposes can be ignored. The weight of the machine and its components is considered to have negligible effect compared to the other driving forces and is not considered. Based on previous studies of the data generated during slurry faced TBM operation only about 20% of the axial force generated by the wheel displacement cylinders is actually directly transferred to the soil (Festa, 2012). Passive forces include the soil and pore water pressure generated at and around the excavation face as well as the shear forces generated by the drag of the spinning cutterhead in contact with the excavation face. Of these forces the net driving force (the thrust forces minus the drag of the mach ine and trailing equipment) and its resulting contact pressures at the excavation face as well as the torque on the spinning cutting wheel and its resulting shear forces on the soil at th e excavation face will be the primary focus in this study. A schematic of the primary forces under consideration is shown in Figure 2 Figure 2 Primary Forces Acting on a TBM Cutter Head in Soil During TBM operation extremely high contact pressures are developed at the excavation face and (due to the buildup of excavated material) inside the working chamber behind the

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11 cutter head. A buildup of excess pore water pres sure in the soil in front of the cutter head will occur as a result of the net driving force. In the case of slurry faced TBM this excess pore water pressure will be partially balanced by the hydrostatic pressures within the working chamber (Festa, 2012). 2.1.3 Clogging of TBMs Clogging can occur in drives with shielded ma chines in clayey soil, especially when using a fluid supported tunnel face and slurry circuit muck ing system. Initially transport of soil in the cutting wheel, excavation area and suction inlet area is hindered (Thewes, 2005). If enough material builds up than stoppages can occur. The problem typically initiates in the suction inlet area when excavated material builds up in front of the inlet grill. The material is th en compressed by more excavated material increasing the contact pressures at the ex cavation face. Eventually the working and excavation chambers fill. Clogging can also occu r in the cutting wheel area, typically towards the center of the wheel. As a consequence, clay discs typically occur in front of the cutting wheel. The clay has to travel from the center (or other location) to the holes in the cutter head to pass into the working chamber. If the excavation face is in mixed cohesive and granular soil stability problems may ensue, particularly when below the groundwater table (flowing condition). Photographs of clogging occurance for both the working chamber and the cutter head face are shown in Figure 3

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12 Figure 3 Photographs Taken from Recent Projects Showing buildup of Clays in The Working Chamber (left) and on th e Cutter Head (right) of a TBM. 2.2 Clay Mineralogy 2.2.1 Formation and Composition of Clays Very fine grained particles such as clays (p article diameter < 0.2micr ons) are a product of weathering and commonly have a crystalline st ructure that contains Silicon (Potassium), Aluminum (iron or Magnesium), Oxygen and Water (Das, 2008). The clay structure is formed by the stacking of octahedral Mg-Al hydroxide molecules to form gibbsite (G) sheets and tetrahedral Si-oxide molecule s to form silica (S) sheets. Covalent bonds hold the ions together in the stacked structure. In Kaolin typ e clays these unit layers are stacked in a oneto-one structure. In Illite and Montmorillinite type clays the unit layes are stacked in a two to one fashion with the hydroxide sheets separated by potassium in the Illites and by water layers in the Montmorillinites as shown in Figure 4 Within the crystal lattice the clay layers are held together by relatively weak Van der Walls bonds due to the polar nature of the particles.

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13 Figure 4 Stacking of clay molecules (from Das, 2008) The surface of every clay soil particle carries a negative charge and the extent of the charge depends on the mineralogy. Due to the presen ce of the two positively charged hydrogen atoms separated by 105 of rotation along one side of it s particle surface water molecules behave as a dipole. The positively charged surfaces of the water molecules attract to the negatively charged surfaces of the clay particles. Due to the attraction and the eventual sharing of the positively charged hydrogen at oms the clays develop what is known as an absorbed layer of surface water. If clay partic les are small and scale-like in shape, the proportion of the absorbed layer by volume becomes high (Terzaghi, 1953). Additionally, cations (typically salt minerals) trapped in th e area near the clay surface will bond with the water molecules and create a second more loosel y held layer of water. Together this forms what is known as the diffuse double layer surrounding clay particles. 2.2.2 Surface Area and Activity of Clay Minerals The size of the diffuse double layer of clay and the intensity of its bond strength is dependent on the surface area of the clay particles. Although numerous different types of clays have been identified in nature three principal groups of clays referred to as

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14 Montmorillonites, Illites and Kaolinites have been used to discuss the differences in clay behavior and mineralogy and will be discussed in greater detail here. Specific surface area is a measure of the clay particle surface area to the mass of the clay particle. All three clay types have a laminated crystalline structure but th eir specific surfaces are very different. The specific surface area of Kaolinite is about 15 m/g, Illite 90 m/g and montmorillonite is 800 m/g (Das, 2008).Surface activity is a measure of the intensity of the surface charge and can be determined experimentally as a measure of the plasticity index of soil to the percent of clay it contains by mass. Normally active soils have an activity of about unity (Terazaghi, 1953). Kaolinites have the least activity fo llowed by Illites which are more active and Montmorrilonites have the most activity and also have the greatest capacity to swell by taking water into their space lattice. A comparis on of the activities of these clay types is provided in Figure 5 Figure 5 Surface activity of common cl ay minerals (from Lamb & Whitman, 1969)

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15 Activity is commonly used as an index for identify ing the swelling potential of clay soils. Clay minerals actively exchange cations (salt mine rals) and water molecules both within the clay structure and externally in the diffuse double layer. The Cation Exchange Capacity (CEC) is a measure of the potential chemical activity of a clay. Some typical ranges for activity and CEC along with other properties for th e common types of clays is shown in Table 1 One method used to quantify the CEC is the methyl ene blue spot method, assuming only the clay fraction is responsible for cation exchange. The resulting electrostatic properties of a clay mineral vary with both cation and water content. A way to measure the cation exchange capacity is to measure the milli-equivalent amou nt of cationic dye that a 100g sample of clay absorbs. Table 1 Comparison of typical Clay Prop erties Atterberg Limits, Acitivity and Cation Exchange Capacity Clay Type LL (%) PL (%) Activity CEC (meq / 100g) Kaolinite 10-110 25-40 0.01 0.5 3-15 Illite 60-120 35-60 0.5 1.0 10-40 Montmorillonite 100-900 50-100 1.0 7.5 80-150 (Data from Grim 1962, Kerr 1951, Lamb e & Whitman 1969, Mitchell 1976) A more direct way of testing for clay minerals susceptible to adhe ring to metal surfaces is to use x-ray diffraction to identify mineral types within the clay.

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16 2.3 Mechanical Properties of Clays 2.3.1 Atterberg Limits As mentioned above the physical properties of clays vary greatly depending on their mineral constituents. Particles are considered to be in a colloidal state when the particles are so small (typically <0.1 microns) that the surface activi ty has appreciable influence on its behavior. Clays have been found to behave as either a so lid, a semisolid, plastically or as a liquid with increasing moisture content (Casagrande, 1932). The range of moisture contents at which soils behave plastically is commonly referred to as the plasticity index. Within the range for the plastic behavior clays exhibit higher shear strength due to cohesion. Cohesion is considered to be a colloidal property and is (likely) due to the increased shearing strength due to the absorbed layers that separate the particles for a clay specimen within the plastic range of moisture contents. 2.3.2 Shear Strength of Clays In a classical strength test such as a shear box test the specimen is subject to a vertical confining pressure and then subsequently forced to shear along a plane within the specimen itself by the application of a horizontal load. It is common to approximate the shear strength of the sample as a linear function dependent on the normal stress applied using the MohrCoulomb failure criteria (Mohr, 1900). The failu re function or envelope is defined by two constants as follows: Where: = shear strength of clay

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17 = cohesion of clay particles = normal load pressure applied to the clay specimen = internal friction angle of clay In testing of clays it is important to distin guish between total and effective stresses. Total stresses act on the clay, water and air (unsaturat ed clays) composite structure and effective stresses are those stresses which act directly on th e solid clay particles themselves. To arrive at effective stresses the value of the pore water pressure is subtracted from the total stresses. 2.3.3 Adhesive Strength of Clays Ideal Adhesion was defined by Meyers (1991) as the reversible work required to separate a unit area of interface between two different materials or phases to leave two bear surfaces of unit area. Practical Adhesion was defined by Zimnik (2000) as the state in which two bodies are held together by intimate interfacial contact in such a way that mechanical force or work can be applied across the interface without causing the bodies to separate. In physical terms clay adhesion is the behavior of clay in which it tends to stick to the surface of other solid materials. Similar to the example given above for determining the shear strength of clays the adhesive strength of clays to a given material can be determined using a modified basic shear box apparatus. The modified testing apparatus is mentioned here to discuss the general adhesive behavior of clay, examples of tests of this kind and the results will be summarized later in the report. Instead of shearing a clay sample along a predetermined plane within the sample itself the clay is sheared along a contact with a metal

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18 (or other material) surface. The results can be presented in terms of a Mohr-Coulomb failure type envelope with the addition of two new constants (Das, 2005): Where: = interface shear strength of clay = adhesion of clay particles to surface = normal load pressure applied to the clay specimen = adhesive friction angle of clay Adhesion and adhesive friction is known to depe nd on the real (vs. apparent) contact surface between the metal surface and the clay (Bowde n and Tabor, 1964). The real contact surface is dependent on the micro-roughness of the surface along with the size, shape and orientation of the clay minerals (Kooistra, 98). True adhesion also depends on the attractive forces between the clay mineral and the metal surface. Consider a steel plate that is wetted and then contacted with a clay particle. Clays with minerals of high swelling potential will ab sorb some of the water that builds up at the steel clay interface. Eventually a suction pressur e with a value similar to pore water pressure will develop in the interface water. Adhesive shear strength can be described in terms of adhesion and adhesive friction angle while adhesive tensile strength is only dependent on adhesion. A model indicating the difference between tensile adhesion (at) and shear adhesion (as) is shown in Figure 6.

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19 Figure 6 Adhesion Model (from Zimnik, 2000) These values are measured using different testing apparatus. The difference between tensile and shear adhesion will be in the real adhesion and differential fluid pressures that develop during the different methods of testing. In adhesive shear strength tests if the shear resi stant forces of the clay to clay contacts are greater than the resistant forces of the clay to metal contact than shearing will occur at the metal (or other non-porous material) surface. If however, the shear resistant forces of the clay to metal contact are greater than the forces of the clay to clay contacts near the metal surface than sticking of the clay particles to the metal surface will occur. Therefore it is possible to predict whether clay adherence to the metal surface will occur if the adhesion, cohesion, adhesive friction angle, cohesive friction angle, normal and shear stresses are known. Based on previous studies, three failure modes for adhesive interface shear have been developed: 1. Sliding along steel clay interface

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20 2. Sliding within clay sample 3. Combination of 1 & 2 Mode 3 has been shown to occur for a certain critical range of steel roughness and involves internal deformation of the clay sample (Zimnik, 2000). 2.3.4 Consistency of Clays & the Effects of Stress History Relative consistency is a measure of the natura l moisture content of a clay specimen in relation to the moisture content at its Liquid lim it and the range of moisture contents over which the soil behaves in a plastic manner. Th e equation for relative consistency is as follows: Using the above formula a clay sample with a relative consistency of zero will be at its liquid limit and at a relative consistency of unity will be at its plastic limit. Henkel (1960) pointed out that there is a unique relationship between the moisture content at failure and shear strength of clayey soils. Platy clay particles in water will have a tende ncy to repel from one another (disperse) due to their negatively charged surfaces. In oversaturated conditions the clays will only be held together loosely by th eir common attraction to the molecules of water and there will be a tendency for the particles to form a lattice like structure with the pore spaces occupied by water. In this way the clay matrix will contain the maximum amount of water possible (Ic = 0) and still behave as a semi-solid mass.

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21 If a normal stress acting on the saturated soil mass is applied the stress will immediately be transferred to the less compressible pore water which will in turn begin to be squeezed out of the mass provided there is a drainage path. This can be thought of in terms of effective stresses acting on the solid clay matrix causing the matrix to compress. The plate like particles will begin to align in horizontal sheets since the weak van der walls forces will no longer be enough to repel the surfaces. If the normal stress is high enough, eventually the all of the free pore water will exit the mass leaving only the solid particles and the bonded water (Ic = 1). The process described in the previous paragraph is commonly referred to in soil mechanics as consolidation. If a clay sample is removed from within the consolidated mass it will have a tendency to lock in the previous consolidation pressures provided the moisture content is kept constant. In this way the relative cons istency and therefore the density, shear and adhesive strength parameters of a clay sample are highly dependent on its stress history. Field observed consistency is a measure of the consistency of clays and is commonly described using terms ranging from very soft to very stiff (Terzaghi, 1952). Due to plastic deformation of clays the real cont act surface will also increase with increasing normal pressure. Along with the type of clays, the degree of co nsolidation will have an effect on the real contact surface area of the clay with a metal surface. Over consolidated clays that exhibit a structure of parallel stacked plates (transverse isotropy) will have a greater real surface area than clays with platy particles in random orientations (normally consolidated) particularly when the stacked plates are also parallel with the metal surface. Therefore, with increasing degree of consolidation it is expected that the adhesion will increase and that the

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22 adhesive friction coefficient will decrease. A model for the increase in adhesion with increasing normal pressure is shown in Figure 7 Figure 7 Theoretical shape of adhesive shear strength envelope based on clay microstructure and real contact area (from Kooistra, 98) In addition, with increasing water content, internal and external bonded crystal water and external free water molecules are present and adhesion is expected to decrease.

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23 3 Previous Studies 3.1 Historical Studies The adhesion limit test in addition to the more commonly used atterberg limits was developed by Atterberg in 1911 for use in the ag ricultural industry. The atterberg limit tests were not widely used in the US for identifying the behavior of fine grained soils until the 1970s. Today the testing procedures for the a tterberg limits for soil are standardized under ASTM guidelines but the adhesion limit test has been left out of the standard. The adhesion limit or sticky limit is loosely defined as the lowest water content at which a soil adheres to a nickel plated spatula when drawn lightly ac ross the soil pastes surface. The adhesion limit always falls between the plastic limit and liqui d limit in terms of moisture content and it separates the range of plasticity, quantified by th e plasticity index, into a sticking range (water contents between the adhesion limit and li quid limit) and a non-sticking range (water contents between the plastic limit and the ad hesion limit). Rieke (1923) defines the limit between the plastic limit and the sticky limit as the Rieke Index. The purpose of the index was to establish the workability of clays for cer amic industry. A Rieke index less than 10 is considered desirable in the ceramics industry. Potyondy (1961) proposed expressing skin fr iction between various soils and construction materials in a form similar to the mohr-columb failure envelope including an adhesion value and a normal stress-dependant compnent. Boisso n (1981) published a graph in which the adhesion of clayey surfaces of plexiglass, leather, smooth steel and rough steel is shown. Also noted was the importance of contact time betw een clay and steel. Kalachov (1975) found a relation between the tensile adhesion and the water content. He determined the maximal

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24 tensile adhesion for each normal stress at the maximal molecular water content, which is the maximal amount of water bonded in th e mineral Skeleton by molecular forces. Littleton (1976) conducted a series of modified shear box tests, similar to those described previously, to assess the adhesion of different clays to a metal surface in shear under various confining pressures and compare with the shear strength of the clays themselves. Shear box and modified shear box adhesion tests were conducted on specimens of kaolinite and illite clays under unconsolidated undrained, consolidated undrained and consolidated drained conditions (Littleton, 1976). To perform the tests a 60mm square shear box apparatus was used. The top face of the shear block, shown in Figure 8 was ground and polished prior to testing and the surface roughness in the direction of shear was measured before and after the tests and the average roughness was found to be 0.18 m (0.00018mm). Figure 8 Modified Lower Half of Shear Box for Adhesion Testing (from Littleton, 1976)

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25 Sample 1 kaolinite was prepared from pow der and the Sample 2 illite obtained from a supplier. Consolidation for the CU and CD tests were done under increasing loads as readings were taken to ensure at least 95% cons olidation had taken place prior to shearing. The strain rate for the CD test was estimated using the method developed by Gibson and Henkel. CU tests were conducted at the ma ximum apparatus speed of 0.592 mm/min. A summary of the results from the CU and CD tests conducted by Littleton are shown in Table 2 below: Table 2 Results of Consolidated Undrai ned and Drained Direct Shear Box Tests & Steel Interface Shear Tests Sample Test PI Peak Friction Angle Peak Adhesive Friction Angle Peak Cohesion (N/mm) Residual Friction Angle Residual Adhesive Friction Angle S2 CU 33 15.0 0 12.5 10.5 S2 CD 33 20.0 18.2 0 14.0 11.5 S1 CU 53 14.8 0.009 S1 CD 53 19.5 17.5 0 14.5 11.5 (data from Littleton, 1976) During shearing the normally consolidated sample 1 specimens contracted. The over consolidated sample 2 specimens dilated at a normal pressure below the pre-consolidation pressure and contracted above the pre-consolidation pressure. The results of the drained tests showed both clays had similar peak stresses but they occurred at different displacements. In the undrained tests samp le 1 typified the behavior of normally consolidated clay and the sample 2 that of an over consolidated clay in which a higher peak

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26 stress is followed by a constant residual st ress. Displacement-Shear curves for both samples at different confining pressures for cons olidated undrained tests are shown in Figure 9 for the normally consolidated kaolinite and Figure 10 for the overly consolidated illite. The increasing slopes of the Sample 1 curves beyond the ultimate strength was attributed to the additional consolidation of the sample (Littleton, 1976) beyond the yield point. Figure 9 Stress Displacement Curves for Undrained Shear Box Tests on Normally Consolidated Sample 1 (from Littleton, 1976)

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27 Figure 10 Stress Displacement Curves for Undrained Shear Box Tests on Overconsolidated Sample 2 (from Littleton, 1976) In both the drained and undrained tests the adhesion of clay to steel was initially higher (steeper slope for stressstrain) than the clay to clay cohesion. It was proposed by Littleton that interface shear values should be repor ted as a percentage of total shear values. Microscopic examination of the steel surface afte r testing revealed minute quantities of clay lodged within the asperities. Observations indicate that 90% of the shearing area consisted of clay to clay contact. It was concluded that the sharp peak stresses at small displacements followed by residual stress (observed on illit e on steel) was due to the history of over consolidation. According to Littleton: The resu lts of the paper suggest that for clay-steel experiments the most uniform adhesion factors ar e obtained using residual shear stress of an over consolidated clay for displacements > 3mm. Interface testing of different construction mate rials and sands of different grain sizes was performed by Yoshimi (1981) using the ring shear apparatus. A specially designed ring shear

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28 apparatus with an inside diameter of 240mm and outside diameter of 264mm was used. A series of stacked acrylic rings were used to confine the sample so that radiographic observations of lead markers placed within the sample could be made. Constant normal stress using steel weights and constant volume tes ts using a hydraulic jack were performed. It was determined that shearing strain during the tests varied as much as 9% with respect to the average due to the difference between the insi de and outside radii. This value reduced considerably after the shear surface had developed. In one series of tests a low carbon structural steel (ASTM A36) was machined to make ringshaped specimens. The lower surface of each ri ng was finished to a different roughness quantified in terms of maximum height (R-max) defined as the largest amplitude along a surface profile over a 2.5mm length The average R-max was between 3 m (0.003mm) and 0.51mm which was considered to cover the ra nge of construction materials. A comparison sketch of different roughness coefficents along with a photo from one of Yoshimisrings is shown in Figure 11 Using an X-ray camera the displacements of the embedded lead markers were measured up to 1 m (0.001mm).

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29 Figure 11 Rmax measurements for different prepared steel surfaces (left). Photo of Prepared Interface Ring Sh ear Surface for Rmax = 220 m (0.22mm) (from Yoshimi, 1981) From the radiographical observations it was c oncluded that the apparatus was successful at producing uniformly distributed shear strains except in a thin zone near the metal surface. Also, at shear stresses less than 85% of the maximum value the sand deforms uniformly throughout its height. Test results at different roughness coefficients from the ring shear testing on Tonegawa Sand are shown in Figure 12 Results from testing of all three samples of sand are shown graphically on Figure 13 The coefficients of friction are primarily governed by R-max of the metal surface, irresp ective of sand density. The coefficient of friction of a very smooth steel surface is 22 to 43% of that of a very rough steel surface. The maximum and residual coefficients of friction are nearly equal when the surface roughness exceeds 0.02mm. This data is in good agreemen t with results reported by others over an Rmax range of 0.01 to 0.02mm for steel. Figure 12 Test Results for Ring Shear Interface Testing Between Steel and Tonegawa Sand for Confining Pressure = 105kPa (from Yoshimi, 1981)

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30 Figure 13 Coefficent of Friction between Different Sands and Prepared Steel Surface for Confining Pressure = 105kPa (from Yoshimi, 1981) 3.2 Recent Studies Thewes (2005) carried out a research program in or der to classify clay formations in terms of their clogging potential for EPBM drives by testing the adhesion of clay on steel. The program was based on practical research regard ing clogging potential as well as laboratory tests with clay samples. A new test was deve loped in order to evaluate adhesion between a soil sample and a steel piston when it is pulled vertically from the sample ( Figure 14 ). The piston surface is wetted prior to contact with the soil. Tmax / Normal Force Peak ( max ) Residual

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31 Figure 14 Schematic of Testing Apparatus used by Thewes to Evaluate sticking potential of clays (Thewes, 2005) Soil-mechanical and mineralogical tests were also performed for comparison with the adhering tests. Information of grain size distribution, natural moisture content and atterberg limits were determined. Adhesion tests were carri ed out with soils from six clay formations varying in their mineralogical composition. Parameters that were varied throughout the testing included: Soil consistency Wetting time before contact Contact time Type of wetting fluid Normal adhesion of soil and steel proved to depend strongly on the c ontent of swelling clay minerals and the consistency of the clay. It was shown that normal adhesion increased strongly with increasing consistency (stiffness). It was determined that this increase had not been described in older research because the we tting of the contact surface prior to shearing had not been done before. Decreased wetting time and increasing contact time led to an

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32 increase in the measured adhesion. The adhesion in Kaolinite clays was comparatively low to that of samples with swelling clay minerals. Thewes proposed a model for the mechanisms which drive adhesion of swelling clays to metal surfaces: 1. Soil is wetted with water under atmospheric pressure. The pore pressure in the clay is much lower than the water. The pressure differential causes the clay to absorb the water and the clay structure swells. 2. A steel plate is wetted and then placed into contact with the so il. There is a small amount of water enclosed in the micro-asperities of the steel when in contact with the soil. The pore pressure differential in the clay allows it to begin absorbing the water. A subpressure similar to the pore wate r pressure in the clay develops in the encapsulated contact water. A resulting tensile stress develops at the interface. During the research program the constructi on details and geological information were collected from several tunnel drives where adhering problems of different types and magnitudes occurred. The machines used in the case studies were not originally designed for clayey soils. Thewes (2005) determi ned that in tunneling in stiff to hard swelling clays the soil typically has to be conditioned using as a supporting medium. In such cases foams are typically added into the working chamber to reduce the effects of adhesion at the face. He also observed that the mucking system which typically consists of a screw conveyor and muck skips on trains is particularly suscepti ble to issues associated with adhesion.

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33 Comparison of the test results with the ne w apparatus, mineralogical and mechanical properties of the samples and information from the case studies le d to a new simplified classification scheme based on the ratio of the relative consistency of in-situ clay to its plasticity index as measured in the laboratory. The chart separates the plot into three zones of low, medium and high clogging potential with low potential leading to a reduction in TBM advancement rates and high potential indi cating significant reduction in advance and daily cleaning of the TBM cutter head. The thewes chart is presented in Figure 15 Figure 15 Evaluation of the Clogging Potential for Clays in Slurry Faced TBM Drives (Thewes, 2005) High Clogging Potential Medium Clogging Potential Low Clogging Potential Soft Medium Stiff Stiff Very Stiff Hard

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34 The Thewes chart is now commonly used in indust ry for predicting the potential for sticking clays to be an issue during the planning stag es of a projects development. The simplicity of the chart and the fact that it uses soil parame ters that are commonly assessed at even the earliest stages of conceptual design make it a very useful tool for engineers and owners. Plasticity is an inherent property of a clay formation which (as shown previously) is directly tied to clay mineralogy and correlates with clay activity. The premise of the chart is that as the water content of a cohesive soil with a hi gher PI (potentially sticky) approaches the plasticity index (Ic=1) the stiffness and the likelihood of clogging issues increase. Following an example of the use of the Thewes method if a sample of clay has moisture content at its plastic limit then the relative c onsistency of that sample is equal to unity. As the moisture content of the sample is increased to its adhesive limit, as defined by Atterberg, the location of the sample on th e Thewes chart will move down corresponding to a relative consistency of less than unity. If the samples moisture content is further increased within the sticking zone on the atterberg chart (within the Rieke Index) the location of the sample will continue to move down on the Thewes chart eventually into the zone of Low Clogging Potential. In this way the use of the Thewes method does not correspond with classical adhesion theory. Following on the techniques proposed by Littlet on, Zimnik (2000) conducted a series of clay-steel interface tests using a modified dir ect shear apparatus. Tests were conducted in a direct shear box with dimensions of 63mm x 10mm at rate 0.1mm/min. The tests were conducted to assess the effects of clay mineral type, roughness of steel surface, contact time and applied normal stress. Two clays prepared from powder: A Speswhite Clay (PI=30)

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35 which was determined to have a fine fraction of 79% (<0.002mm by mass) and composed mainly of the clay mineral Kaolinite. Also a sample of Boom Clay (PI=31) was determined to have a fine fraction of 71% and composed of quartz, illite, kaolinite and other trace minerals. The samples were consolidated first in an odometer then again in the direct shear apparatus. In this fashion all samples were considered to be normally consolidated prior to testing. Tests were typically carried out under consolidated undrained conditions in accordance with the procedures outlined in ASTM D-3080. The normal loads were varied at least up to the loads existing at the tunnel face and in the mixing chamber of the TBM. Various steel plates with different roughness coefficents were prepared for the testing by varying the intensity of sparkling at the surface which creates an isotropic roughness (Zimnik, 2000). It was found that the adhesive shear strength increases linearl y when it is plotted as a function of normal stress between 0 and 500kPa. The adhesive strength of both clays was found to vary with slight variation in the roughness of the plates as can be seen on Figure 16 The effect is more noticeable at higher confining pressures. According to Zimnik, this is due to the fact that increasing the normal stress and with increasing roughness more internal deform ation takes place, causing strain hardening. At this point shearing will be more likely occur within the sample rather than across the interface with the steel. For both clays a critical roughness between 2.4 and 4.7 m was observed. The Speswhite also showed higher ad hesive strength values than did the Boom clay likely due to the effects of the different mineral constituents.

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36 Figure 16 Influence of Roughness in Di rect Shear Adhesion Tests with Contact Time of 1-Hour (Zimnik, 2000) The influence of contact time is presented in a similar manner in Figure 17 The lowest roughness steel plate was chosen for these tests to ensure that shear was occurring at the contact and not within the clay samples. Contact times included consolidation time in the direct shear box. Generally it was observed that an increase in adhesive shear strength was found with an increase in contact time particularly at higher normal stresses.

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37 Figure 17 Influence of Contact Time in Direct Shear Adhesion Tests, Steel plate with roughness of 0.2 m (Zimnik, 2000) The moisture content of the samples were measured before and after each test to compare soil consistencies. Before and after shearing th e water content of each sample was above the plastic limit. After the test the consistency index for each clay increased which would lead to an increase in the adherence potential. At higher normal stresses this feature is more pronounced.

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38 In a similar series of tests Kooistra (1998) ex panded the clay sample pool to investigate more thoroughly the contributing factors to adhe sive shear strength. A commercial potters clay (K122); a kaolinite (China clay); the drilling mudnam ed bentonite, but actually consisting of the clay mineral sepiolite (instead of mont morillonite); a Boom clay, a type in which tunneling and underground construction has occurred in Belgium and which will be excavated in the Westerschelde tunneling proj ect; Kedichem clay, which has recently been excavated during tunneling near Heinenoord (Rotterdam); Eem clay, a clay which will be excavated in the Noord-Zuid tunnel project in Amsterdam. On the samples dry volumetric weight, water content, grain size distribution by wet sieving, Atterberg limits (liquid and plastic limit) and the Cation Exchange Capacity (CEC) using the mrthylene blue spot method were determined. Samples of the normally consolidated potters clay (K122, PI=33,A=0.62, Ic=0.73) and over consolidated Boom Clay (PI=50, A-0.93, I c=1.06) and Kedichem clay (PI=26, Ic=0.35) were tested in the shear box 100x100x12mm mo dified for adhesion testing. The clays were sheared at a low rate of 0.5mm/min over a part ially rusted metal surface. The metal surface was chosen to increase the real contact area with the clays and to mimic TBM cutting tools. The tests were carried out under consolidated undrained conditions, following the procedures outlined in ASTM D-3080-90. Th e normal loads were carried up to 500kPa a range relevant to the pressures existing in the mixing chamber of the tunnel boring machine of the second Heinenoord tunnel. The results of the shear box tests are shown in Figure 18 For the normally consolidated clay at its natural moisture content the adhesive shear strength was constant at 9kPa for low

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39 normal stresses, above 25kPa normal stress the ad hesive shear strength increased linearly. For the overconsolidated clays at natural wa ter content and low normal stress the adhesion was very low and only adhesive friction appear ed to contribute. At higher normal stresses (between 70 and 100kPa) the apparent adhe sion was higher and reached 30kPa for the Kedichem clay and 80kPa for the Boom clay. Figure 18 Results of Modified Shear Box Tests (from Kooistra 1998) Further testing to evaluate the effect of th e moisture content was performed on the normally consolidated potters clay (K122). Shear box adhesion and traditional cohesion tests were

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40 carried out in the same manner at low normal stress between 25 and 55kPa. In this study the peak cohesion was found closer to the plastic limit than the liquid limit. Also from the results, according to Kooistra: It can be seen that for this clay cohesion is higher than adhesion for all water contents and that cohesion exponentially decreases with water content. It was suspected by Kooistra that the results were indicative of the Kaolin type clay tested and that values of adhesion that exceed the cohesive shea r strength of a clay sample at a particular moisture content may be found with the testing of clays with higher activity values. 3.3 On-Going Research Another test developed for the purpose of quantif ying the stickiness of clays is the cone pull out test apparatus (Feinendegen et al, 2010). For the test the clay is compacted into a standard proctor mold and a cone shaped hole is predrilled into the top of the sample. A cone which fits the size and shape of the hole is inserted into the cavity and loaded for a period of 10 minutes with an applied pressure between 3.8 and 189 kPa. The load is the removed and the cone is pulled out at a velocity of 5mm/ min as the tensile force and displacement are recorded over time. Several di fferent cones with inc linations ranging from 10 to 73 have been developed for the test as shown in Figure 19

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41 Figure 19 Cone Pull Out Testing App aratus, developed by InProTunnel Working Group (from Feinendegen et al, 2010) In some preliminary testing performed by Spagnoli (2010) he found that the maximum tensile stress for the overconsolidated Wester wald clay (Ic=0.7) wa s generated at a cone displacement of about 2mm for all cone inclinations. For the apparatus with cone inclination between 30 and 45 the maximum tensile stress on the cone was above 20kN/m and approached zero at about 5mm of displacemen t. For cone inclinations between 55 and 75 a maximum tensile stress of about 16.5 kN/m was generated and tensile forces continued to be measured at 10mm of displacement or more Further testing was performed to test the effect of the water content of a soil to the pu ll out resistance. Soil consistencies between 0.2 and 0.85 were tested. For low consistencies below 0.6 tensile stresses were measured over a relatively large cone displacement of 20 to 25mm and reached a maximum tensile stress of about 11kN/m. For consistencies above 0.6 the curves of tensile stress Vs. displacement becomes much steeper and the maximum stress recorded for a consistency of 0.85 was 24.5kN/m. Results of the tests are summarized in Table 3

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42 Table 3 Cone Pull Out Test Results Tens ile Strength Vs. Displacement for a cone inclination of 58 degrees and an overconsolidated clay Consistency Maximum Tensile Strength Displacement at Max Tensile Stress Maximum Displacement of nonzero Tensile Stress Total Pull Energy Total Adherence 0.2 2kN/m 8mm 24mm 28kNmm/m 290 g/m 0.4 8kN/m 7mm 22mm 102kN mm/m 770 g/m 0.55 11kN/m 4mm 14.5mm 88mm/m 600 g/m 0.7 16.5kN/m 2mm 10mm 63mm/m 530 g/m 0.85 24.5kN/m 1mm 5mm 25mm/m 70 g/m (data from Spagnoli, 2010) A new classification scheme was developed for assess the potential stickiness of clays based on the relative consistency using the cone pull out device. The proposed system is shown graphically in Figure 20 A good correlation was found between the total pull energy (integral of the Consistency Vs. Pull Energy cu rve) and the Adherence which is determined by weighing the amount of clay that is stuck to the cone apparatus once it has been extracted from the sample. For the study adherence values less than 150 g/m were considered to indicate a low clogging potential and values measured above 300 g/m indicated a high clogging potential. The highest pull energy and adherence where found at a relative consistency of 40 to 60% and the adherence va les remain in the zone of high clogging potential over a consistency range of 25 to 75%.

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43 13) Westerwald Clay, 14) London Clay 15) Boom Clay, 16) Smectite ClayFigure 20 Proposed adherence Classifica tion System based on the Cpone Pull Out Test (from Spagnoli, 2010)

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44 4 Industry Experience and Case Studies The first step in dealing with sticky clays along a tunnel alignment is to identify the extent of the potential issue in the preliminary design pha ses. A desktop study should be performed at the earliest stages of developing the proj ect concepts in order to obtain geological information to identify the likelihood sticky clay deposits. This information could be particularly useful as part of the trade-off study of choosing potential methods (trenchless Vs. cut and cover) and horizontal and vertical alignments. Next, during the preliminary design stages investigation techniques, field obs ervations and simple laboratory index testing can be used to identify the potential for clo gging to be an issue. For advanced studies a mineralogical analysis to identify the relati ve percentages of diffe rent minerals such as Kaolinite, Illite and Montmorillonite with in the alignment can be performed. The Thessaloniki Metropolitan Railway project is comprised of two separate 6 meter diameter tunnels over an 8 kilometer stretch in Greece. The tu nnels will be excavated with the use of two EPBM machines. The geology consists of gneiss bedrock overlain by Miocene to lower Pliocene stiff to hard clays an d silty clays and Quarternary alluvial gravels, sands and clay deposits. The tunnel alignmen t encounters the red clay and silty clay deposit mainly. The consistency of the clay deposits along over 50% of the alignment consists of stiff to hard clays. The potentia l clogging risks to the TBM were evaluated based on the Thewes method ( Figure 21 ) discussed previously and a system used by GeodataTorino (Figure 22 ). For the Athens Metro Line 3 exten sion project the potential for sticky behavior was based on a relationship between the ratio of natural moisture content to plastic limit and the plasticity index. Using all of the data from the Thessaloniki Metro the Thewes

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45 method indicates a medium to high (72% of data points) TBM clogging potential and the Geodata-Torino method indicates a low (70% of data points) clogging potential. Figure 21 Clogging Risk of Thessaloniki Metro based on the Thewes method (from Marinos, 2007) Figure 22 Potential for Sticky Behavior of Cohesive Soils of Thessaloniki Metro based on the Geodata-Torino method (from Marinos, 2007)

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46 The Beacon Hill Project in Seattle Washington, was a transit tunnel excavated in Glacial Till from 2005 through 2009 using an EPBM. As part of the design adhesion limit tests along with Atterberg limits and natural moisture content testing were performed. All of the natural water content testing placed the materia l below the adhesion limit indicating the clays were not prone to sticking. Although not considered at the time, computing the consistency and plotting it against the plasticity index usi ng the Thewes method indicated a potential for some of the soils to include sticky clays. Ultimately the tunnel was specified to include up to 25% of potentially sticking material due largel y to the clients past experience with similar projects. After construction commenced the adhesion of clay was observed in the cutter head, screw conveyor and muck conveyor. After identifying the clay bearing units within a planned tunnel drive and the magnitude of the stickiness of the clay, TBM manufactures ca n use this information to optimize some of the components on a new or refurbished tunnel boring machine. Some of the methods that have been shown to work well in the past include (Thewes, 2005); spreading out cutting tools to create larger soil chips which reduces adhesive surface to volume ratio of spoils; enlarged passages for soil transport from tunne l face to the screw conveyor or slurry line; increased agitation in areas prone to settlemen t which prevents agglomeration; use of open spoke like cutting wheels which decreases the amount of metal surface in contact with the excavation face; smooth out sharp angles within the excavation chamber and; include an independent active center to the cutting wheel which can be turned at a higher rotational speed. When issues arise during TBM advancement either planned or unplanned the contractor can; reduce the advancement rate; replace worn tools and surfaces; maximize

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47 suspension flow rate; flush the excavation cham ber; operate under partial air support and; add chemical additives to the slurry. For the Subway Essen Lot 34 completed in Germany in 1990 (Wayss, 1995) a 8.3m (27ft) diameter slurry TBM was a used. The slurry shielded TBM was chosen to limit surface settlements in some of the soft cohesive soils. To handle potential clogging issues in the stiff cohesive soils conditioning agents injected in th e slurry along with the first ever use of an independently spinning center cutter. A photo of the independent cen ter cutterhead is shown on Figure 23 The center cutter acts as its own separate TBM running in EPB mode and discharging into the working chamber. Figure 23 Independent Cutter Head Used in TBM on Subway Essen Lot 34 Project (from Waays, 1995) The Westerschelde Tunnel in Netherlands was considered a landmark project in the evolution of the TBM machine to handle stic king clays in a weak rock formation (Sagar, 1999). As part of the design a geotechnical ev aluation was performed specifically to assess the clogging potential of the alignment soils which were identified in over two thirds of

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48 tunnel drive. Two Herrenknect mixshield TBMs were used to complete the transit tunnel in a Tertiary aged, overconsolidated, highly plastic (illitic-montmorillonitic) Boom clay. The machines included optimized cutting wheels, excavation chambers and suction inlet areas and a sophisticated flushing system that used a data acquisition system to optimize slurry concentrations and recirculation rates. Sp ecific features of the TBMs were open spoked cutterheads with streamlined cutting arms and soft ground cutting tools, individual feed and slurry lines, excavation chambers lined with s teel sheets to avoid clogging prone angles and rotary ( as opposed to jaw) crushers equipped wi th agitators inside the inlet suction area. Additives are commonly used, particularly in slurry faced TBM drives to reduce clay adhesion at the face and in the return line. As previously explained the diffuse double layer between clay particles within a clayey material is made up of both absorbed water and free water that contains salt molecules (cations). B ecause clay particles are negatively charged on their surfaces but contain positively charge water layers clay molecules include both attractive and repulsive forces towards one anot her. Anti-clay additives serve to increase the electrostatic repulsive force between clay particle s by adding additional anions to the diffuse double layers which separate the particles. Sin ce cohesion is related and thought to be a direct result of the attractive forces created by the shared water layers, increasing the repulsive force between clay particles will d ecrease the influence of cohesion on the shear strength of the soils. The Silicon Valley Rapid Transit (SVRT) is an extension onto the existing Bay Area Rapid Transit (BART) system included five miles of twin bore tunneling in San Jose California (Ball, 2009). The preferred tunneling method was to use an Earth Pressure Balance Machine

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49 (EPBM) through the clayey soils. As part of the design a sample of high plasticity clay with trace sand was retrieved from one of the s onic borings. The samples were supplied to the laboratory at BASF chemical company for testing of the effectiveness of different soil conditioners. The soil was divided into smalle r samples and different ratios of water, foam and anit-clay agents were added to the samples and blended with a metallic mixing paddle. The amount of clay adhering to the paddle al ong with observations on the way in which the clay covered the windows within the paddle surfa ce and the amount of work required to spin the paddle were recorded (Ball, 2009). The preferred ratio of water and the different conditioning agents were determined prior to the commencement of TBM excavation. For this project a mixture of additional water, anticlay admixtures and foam was chosen. Foam which when combined with air expands when agitated further increasing the clay dispersi on and thereby reducing the shear stress needed to break the bonds between clay particles. From this testing it was observed that a mixture of 7.5% by weight of water, 1.5% of Rheosoil 211 (BASF Inc.) a water soluble deflocculating agent and 30% foaming agent for bulking the soil mix to cut down on torque was optimal at reducing adhesive strength and total adhesion to the mixing paddle. The Bay Division Pipelines Reliability Upgrade Pr oject is an upgrade to the existing water system which serves residential customers in the city of San Francisco (Ericson, 2005). One component is the Bay Division Pipeline a 21 mile long pipeline that includes a tunnel (Bay Tunnel ) under the San Francisco Bay. The Bay Tu nnel will consist of a 108 inch internal diameter pipeline extending 5 miles under the San Francisco Bay, adjacent marshlands and Salt Ponds. Due to environmental concerns only a launching and receiving shaft will be

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50 constructed and the entire tunnel length will ne ed to be completed in one drive. The tunnel depth ranges between 70 to 100 feet below the mean surface of Sand Francisco Bay. The tunnel is to be constructed as a two pass syst em and the initial pass will include the erection of precast concrete segments immediately be hind the pressurized face TBM. Geologic conditions include marine deposits including younger (soft) and older (stiff to hard) silty clays, alluvial deposits including beds of medium stiff to hard silty clays and highly weathered sedimentary and metamorphic rocks. A EPBM was selected as the most appropriate ma chine for the ground conditions due to the high percentage of cohesive soils. The ability to inject foam (foaming agent and air) into the working chamber to stabilize the ground and reduce the torque required to cut the ground thereby reducing the cutter wear was an important factor to choosing TBM types. Polymers and dispersants added to the foam water mix will be used to reduce the potential for the highly plastic soils to stick to the metal cutter head and screw conveyor. Another goal of optimizing ground conditioner application is to reduce cutter head torque and abrasion which is particularly important in this long drive with no intermediate access. Frequent inspections of the cutting tools will be implemented particularly in areas of high likelihood of wear.

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51 5 Description of Testing Program 5.1 Previous Laboratory Testing Programs Previous studies related to interface testing between clay and steel surfaces have been performed primarily with the use of a modified direct shear device or more advanced testing equipment designed specifically for testing cer tain parameters. The direct shear apparatus, utilized by Litttlejohn (1976) for clay-steel interfa ce testing, is easy to operate but it has a number of disadvantages, most important of wh ich is that shearing stresses and strains are not uniformly distributed over the contact sur face which causes progressive failure beginning at the ends of the soil specimen. Additionally, in order to determine the residual strengths of clays the direct shear device has to be reversed several times before the failure surface is fully established. Following on the techniques propos ed by Littleton, Zimnik (2000) conducted a series of clay-steel interface tests for applic ations specific to tunneling using a modified direct shear apparatus. Zimnik chose a rang e of confining pressures and steel surface roughness coefficients similar to what had b een observed in some recent TBM drives. For both clay samples tested a critical roughness coefficient between 2.4 and 4.7 m was observed, above which shearing was likely to occur not at the interface, but within the sample itself. Yoshimi (1981) created a custom ring shear device in order to perform interface testing between common construction materials and diff erent sands. The apparatus used to stacked acrylic rings to allow for the tracking of le d markers that were embedded within the sample. Based on led marker movement tracking he deter mined that shearing strain varied by less than 10% from the average between the inside an d outside radii of the ring sample and that value reduced considerably after the shear surface had developed. For his tests Yoshimi

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52 quantified the R-max value as the largest amplit ude if change over the ring surface profile and he determined the range of R-max values was 3 m (0.003mm) and 510 m (0.51mm) for construction materials. Other similar type ex periments were conducted with R-max values ranging from 10 m to 20 m (0.01 to 0.02mm) for steel. Traditionally, ring shear tests are the recomme nded method for determining the values for the drained residual strength of clays. The benefi ts of the ring or torsion shear apparatus are: the sample width is small in relation to its diameter which provides very low variations in strain across the width of the sample, the shea ring can take place continuously in a single direction so the machine does not require reversal to develop a failure surface and to measure residual strengths. For clays, this allows for more complete platy particle orientation along the shearing plane, and a more accurate measurement of the drained residual strength than would be achieved in tr aditional direct shear or triaxial tests (Bishop et al., 1971). The ring shear test is suited to the relatively rapid determination of drained residual shear strength because of the short drainage path through the thin specimen, and the capability of testing one specimen under different normal stresses to quickly obtain a shear strength envelope. 5.2 Clay Sample The clay sample used for the laboratory testin g program is a white Kaolin Ball clay extracted from the Kentucky portion of the Mississippi Embayment (Mid-Late Tertiary). The clay was obtained, dried, ground to a powder and supplied by the Old Hickory Clay Company based out of Mayfield, KY. The clay used for the laboratory testing program has

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53 the properties shown in Table 4 which are typical propertie s based on a rigorous quality assurance-quality control program and wer e provided by the manufacturer. Table 4 Properties of Kaolin Cl ay (Old Hickory Clay Company) Property Unit Average Value (Range) Particle size, %Finer than 75 m % 100 10 m % 90 1 m % 60 0.5 m % 50 Cation Exchange Capacity Meq/100ml 9.0 Specific Gravity (2.40 2.65) pH 6.0 (4.0 8.0) Silicon Dioxide content % 60.5 Aluminum Dioxide content % 26.5 The primary benefit of using a test sample reconstituted from powder is to avoid any influence from preexisting consolidation pressures. In addition it makes moisture conditioning to a certain percentage simpler. Atterberg limits of the sample were estimated based independent testing by the author. Five separate tests were conducted to determine the plastic and liquid limit and the correspondin g plasticity index in accordance with ASTM D4318. The estimate of the stickiness index is based on the original test method proposed by Atterberg and is an estima te taken for comparison purposes. Results of atterberg limit testing are presented in the Section 6

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54 5.3 Consolidation Testing Prior to conducting the modified ring shea r tests the consolidation parameters of the remolded specimens were estimated by conducti ng several consolidation tests in accordance with ASTM D2435. The consolidation testing apparatus consisted of the consolidation device which includes the sample ring, porous stones, filter paper, water reservoir and loading plate in addition to the dial gauge and sample preparation tools. The consolidation testing device used was made by Wykham-Ferrace and is shown as an image in Figure 24 Figure 24 Photograph of 1-Dimens ional Wykham Ferrace Consolidometer The sample was wetted to moisture content j ust above the liquid limit and remolded into the loading chamber. The weight of the dry and wet sample was measured along with the precise dimensions of the sample chamber in order to calculate the density of the sample. The sample was placed into the sample chamber and the vertical deformation gage set to zero. Loads were then applied to the sample using the weight counterbalance system of 1:10 ratio. The loading schedule included applied pressures to the sample of 0.25, 0.5, 1.0 and 2.0tsf. A stopwatch was started at the same mo ment loading was applied in order to take

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55 accurate measurements at time intervals of le ss than 30 minutes. Deformation readings were taken at intervals of increasing duration throughout the consolidation phase in order to define the deformation vs. log time curve to appropriate detail. ASTM D 6467-99 provides standardized guidance for sample consolidation for drained ring shear testing of cohesive soils based on the re sults from the consolidation tests. Results of 1D consolidation testing are presented in Section 6 5.4 Bromhead Ring Shear Apparatus The testing program was conducted primarily with the use of the Bromhead ring shear apparatus, WF25850 (Bromhead, 1979) built by Wykeham Farrance Engineering Ltd. The device used for the testing is shown in images in Figure 25 The manual for the ring shear apparatus is included as an Appendix A to this report. Figure 25 Photographs of Wykham Ferrace Ring Shear Apparatus

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56 To use this apparatus a ring shaped soil specimen 5mm (0.197in) thick with an inside diameter of 70mm (2.756in) and an outside di ameter of 100mm (3.937in) is molded into place in the sample chamber. The sample is then confined between two (top and bottom) concentric rings. The rings that are supplied wi th the testing apparatus are made of a porous bronze material that has been rigged on the surfa ce which is in contact with the sample. In the traditional test the sample is meant to shear not at the interface with the ring but within the sample itself. Confining pressure is provid ed by a counter balance system with a 10:1 ratio of applied load to weight added. Metal weights are also provided that relate to standard pressure increment. A rotation is imparted to the base plate and attached lower platen by means of a variable speed motor and gearbox driving through a worm drive. Measurements of sample vertical displacement are made by means of a sensitive dial gage bearing on the top of the load hanger. Torque transmitted thro ugh the sample is measured by a set of twin load measuring proving rings located on either side (North-South) of the sample chamber and bearing on a cross arm attached to the top plate and upper platen. 5.5 Modified Ring Shear Interface Test The main phase of the testing program is a seri es of consolidated undrained or Quick ring shear tests which should most accurately simula te conditions at the soil-cutter head contact in a TBM tunnel. Due to the rotational speed at which the cutter head moves against the soil when operational it is unlikely that a drained state is reached in a typical construction scenario. The primary purpose of the testing program is to evaluate how the adhesive shear strength of clays to metal surfaces changes and is related to: Clay consistency, Micro-Roughness of the steel surfa ce in contact with the clay,

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57 Normal force, and over consolidation ratio of the clay specimen. In order to modify the Bromhead Ring Shear Apparatus several steel rings with different levels of micro-roughness were machined to se rve as a replacement for the top and bottom brass rings that are available with the ring sh ear device. For the top ring two separate steel rings were machined from a solid steel disk of multipurpose (low carbon, industrial) stainless steel. The solid steel disk(s) were obtained from McMaster-Carr industrial supplier. The specifications of the steel disks and the mach ined top and bottom rings are provided in Appendix B of this report. From the steel disks, solid steel rings with the same dimensions as the top wing provided with the ring shear device were machine cut and drilled so the rings could be secured to the top plate of the Brom head Ring Shear device. The dimensions and roughness details of the modified stai nless steel top rings are shown in Figure 26 Photographs of the two rings used fo r the interface testing are shown in Figure 27 The two different rings with R-max values of 2m (0.002mm) and 20m (0.02mm) were used to conduct the interface testing. The ro ughness coefficents were chosen because they represent a range of roughness coefficients for steel interface testing c onducted in the past (Littlejohn, 76, Yoshimi, 81, Kooistra, 98, Zimnick, 00). Every attempt was made to maintain the integrity of throughout the testing program so as to change the roughness over time.

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58 Figure 26 Schematic of Top Steel Rings

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59 Figure 27 Photographs of Top Stainless Steel Rings In addition to the top ring modifications, it was learned from trial and error early in the testing program that the bottom or base ring supplied with the Bromhead apparatus had to be replaced with a stainless steel machined ring as well. The details as to how this conclusion was drawn are presented in the results section of this report. Similar to the top rings, a bottom ring with an average surface roughness coefficient of 250m (0.25mm) was manufactured and secured to the base plate of the ring shear apparatus. A schematic of the bottom or base ring can also be found in Appendix B of this report.

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60 5.5.1 Modified Ring shear Assembly Procedures: The procedures for assemblage of the ring shear device (assuming the primary assembly of the motor, gear box, and worm drive has already taken place) is performed in the following steps: 1. Remove the sample chamber and the torque arm assembly from the sample bath by removing the locking screws and using the lifting screws to move 2. Remove the torque arm assembly from the sample chamber using the lifting nuts. 3. Remove the bottom brass ring from the ch amber by unscrewing the four screws. Replace the ring with the steel ridged and roughed bottom ring using the same screws. 4. Remove the top ring brass ring from the torque arm assembly in the same manner. Replace the ring with one of the t op steel ring with known roughness 5. Reassemble the sample chamber and torque arm assembly and replace in bath by center pin. Reattach with clamping screws. 5.5.2 Sample Preparation Procedures: The sample preparation includes reconstituting the clay by adding and thoroughly mixing water with the clay powder and molding the reconstituted clay sample into the ring shear sample chamber. These activities are performed following these steps: 1. Measure the mass of a metal dish. After, place enough clay powder in the dish to fill the ring sample chamber once sample is hydrated. 2. Measure the mass of the metal dish and th e sample combined. Calculate the amount of distilled water to add to the sample using the following formula (assuming pre-test

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61 moisture content of 70%) and add the water in a controlled manor so as not to cause splashing. 3. Thoroughly mix the powder clay sample wi th the water using a rounded end spatula capable of maintaining contact with the sides of the bowl. Mixing will involve circular motions with the spatula as well as downward (squeezing). The goal is to expose all of the clay mineral surfaces to th e water. Mixing should continue until the consistency of the clay is homogeneous at wh ich point it should behave similar to a wet putty. 4. Make sure the ring shear device is level 5. Moisten the bottom ring of the apparatus enough to completely cover the surface with a film of water but not so much that it will dramatically affect the moisture content of the sample 6. Carefully place the hydrated clay in the ring chamber on top of the bottom ring. First using the small rounded end spatula place the clay in clumps or balls around the perimeter and in the corners of the ring chamber. This will help to avoid any voids from forming in the sample. 7. After the bottom ring is completely covered with sample and there is good contact everywhere on the ring, begin placing additional hydrated clay sample in the chamber until the top collar of the chamber is reached. Use the flat ended spatula to work the clay sample into the chamber and to strike off excess sample above the collar so the top of the molded clay sample is even with the top collar.

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62 8. Wet the top ring that is attached to th e torque arm similar to the how the bottom ring was wetted. Carefully place the torque arm over the sample, centering it on the centering pin. Do not drop the torque arm onto the sample. 9. Move the loading yoke so the loading bolt is centered on the receiving plate of the torque arm. Turn the loading bolt as necessary to achieve good contact. 10. Swing the vertical displacement gage and tighten its holding bolts so it is centered over the loading bolt and has good vertical contact with the top center of the bolt. Tighten the holding bolts so the ga ge wont move during the test. 11. Submerge the sample chamber by filling the water bath with distilled water. 12. Shortly after submerging the sample, apply a seating pressure to the sample to prevent swelling. The seating pressure can be applied using the 0.25tsf (calibrated for 1:10 load arm) weight. 13. Load the sample according to the loading schedule to allow for complete and homogeneous consolidation at each of th e given pressures. Do not overload the sample at any given time step before the complete consolidation has been reached from the previous time step. 14. If conducting an Over-consolidated test remove loads in accordance with the correct time sequence and allow enough time for complete swelling to occur at the given load. 15. Record vertical displacements at increm ents for the consolidation and swelling phase(s).

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63 5.5.3 Interface Ring Shear Testing Procedures: Once the ring shear device has been modified with the stainless steel rings (Section 5.5.2), interface testing of the consolidated clay sample is conducted in the same manner as a normal undrained shear strength test in the ring shear apparatus. The procedures for testing are as follows: 1. Measure and record the mass of a clean, dry metal dish and set it aside until after the shearing phase is complete. 2. Prior to engaging the ring shear drive moto r make sure the sample has been prepared and is fully consolidated (normally or overly). 3. Swing the proving ring turret (North or South) into position by loosening the locking nuts at the base of the turrets. The provin g ring assembly is in correct position when the bearing rods are perpendicular with the torque arm loading plate facing the ring turret. 4. Unscrew the bearing rod to extend it unt il the rounded end is in intimate contact with the torque arm loading plate. Be careful not to apply excess force on to the torque arm as this could lead to some pre-shearing of the clay sample. 5. Repeat steps 2 and 3 for the other proving ring turret. 6. Zero the vertical displacements gage an d the two proving ring displacement gages prior to engaging the drive motor. 7. Adjust the drive motor gear lever setting (A through E) to the correct position and replace the gear wheels within the gear box manifold to the correct ratio for the desired ring sample chamber rotational speed. For undrained tests use a ring speed of at least 0.5mm/min. The conversion of rotational speed to corresponding translational speed at the center of the ring sample (Mean Diametrical length = 85mm) is as follows:

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64 In order to ensure undrained strength properties use a translational speed of at least 1.5mm/min = 2.0deg/min. (For safety use 3.0deg/min corresponding to gear lever position of B and a gear ratio of 30:60) 8. Plug in the Ring Shear Device. Confirm power is reaching the drive motor by the light next to the power button. Make sure th e sample bath is topped off and all gages are still set to zero before turning the device on. 9. Start a timer at the same time the power button is pressed down. Once the power button is suppressed begin recording observations at each degree or rotation for vertical displacement and displacement (load) on the proving rings. Also record the peak displacements (loads) on each of the proving ring assemblies. The specific ring shear device used is not equipped with a real time data logger. Depending on the rotational speed chosen in Step 7 it may be necessary to engage the services of an assistant or a video recording device mounted on a tripod in order to record both proving ring displacements and the vert ical displacement simultaneously. 10. After the test in under way take occasional readings of the timer (minutes and seconds) just prior to gage readings and r ecord the elapsed time in order to confirm the rotational speed is as expected. 11. Continue taking measurements until long after the peak shear resistance has been reached and far enough into shear displa cement to confirm the residual interface shear strength properties. A good rule of thumb is to continue taking measurements for at least 20 degrees past the peak shear resistance of the sample. 12. After residual shear resistance is confir med (I.E. additional rotational displacement does not cause additional load on the prov ing rings) stop the test by pressing the

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65 power button next to the gear box assembly. The ring chamber should stop rotating and loads on the proving rings should immediately decrease. 13. Disassemble the ring shear device by first ro tating the proving ring turrets out of the way and removing hinge nuts from the sample chamber. Remove the vertical load by unloading the lever arm, swinging the vert ical displacement gage out of the way and removing the loading yoke from the loading bolt. 14. Carefully lift the sample chamber by the lifting screws and transport the entire sample chamber to the sink (or another drain). 15. Carefully remove the upper torque arm (and top ring) assembly from the sample chamber by lifting. Note some additional adhesion will have redeveloped between the top steel ring and the top of the clay sample in the time since the shearing has ended. In some cases where large confining pressures were used it may be difficult to remove the torque arm assembly. In those instances a small amount of torque may need to be applied to force the sample to release the top ring. In doing so be careful not to introduce and additional water to the clay sample. 16. Remove the clay sample from the ring shaped sample chamber with the help of a thin metal spatula and carefully place the clay in the sample dish from Step 1. Again, be careful not to introduce additional water to the sample or in the dish as this sample will be the basis for the end of test moisture content measurement. 17. Weigh the sample dish and the wet sample an d place the dish in an oven of at least 110 F for drying of a period of at least 36hrs. 18. Thoroughly clean the sample chamber incl uding the modified steel rings and begin drying the rings immediately to prevent any deterioration by oxidation from occurring to the ring face(s). Also clean th e Ring shear device water bath container as

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66 some of the clay particles will have inevitab ly settled to the bottom of the tub during the consolidation phase. Place the assembly in a dry location out of the way until another test sample is ready to be prepared. 19. After an appropriate time has passed (the ov en sample is dry) weigh the sample dish and the now dry sample, record the mass and calculate the moisture content of the sample after the test.

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67 6 Results of Testing Program 6.1 Atterberg Limits Atterberg limits are simple tests that were developed to establish the moisture content of fine grained materials at certain consistencies of the clay-water mixture. Procedures for determining the plastic limit and liquid limit of a clay sample are established in ASTM D4318. The liquid limit of the Kaolin sample was estimated using the multipoint technique (method A) as described by the standard. Four different specimens were prepared at slightly different moisture contents near the liquid lim it. A value of the liquid limit for the sample was determined based on interpolating between the number of drops of the Casagrande device required to close a groove in the sample s, to estimate the standard 25 blows. Two separate samples of two ma sses of clay each were used to estimate the moisture content at which a thread of clay 1/8 in diameter co uld no longer be rolled. In addition to these standard tests the stick limit of the clay was estimated by successively adding small amounts of water to a dry sample until the cl ay adhered to a steel (as opposed to nickel) spatula that was passed lightly over the hydra ted clays surface. The results of the Atterberg limit tests are shown in Table 5 Table 5 Summary of Atterberg Limit Tests Atterberg Limit Moisture Content Range Value Plastic Limit 25.0% 25.9% 25.5% Liquid Limit 53.1% 59.8% 57.6% Sticky Limit NA 35.5%

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68 Based on the results of the Atterberg limit tests the indices, or moisture content range over which the clay will behave in a certain manner, can be determined. The plasticity index of the Kaolin sample was estimated to be 32.1% with a range of 27.2% to 34.8%. The Rieke index was estimated to be about 10%. 6.2 1-D Consolidation Testing In order to determine the consolidation properties of the clay sample a 1-D consolidation test was performed in accordance with ASTM D2435. The standard covers the procedures for determining the magnitude and rate of consolidation restrained laterally and drained axially. A sample of the Kaolin clay was prepar ed from powder at moisture content near its liquid limit. A loading schedule including the pressures used for the ring shear test; 0.25, 0.5, 1.0 and 2.0tsf was used for the consolidation testi ng. Measurements taken during the test for each of the load increments are shown in Appendix C Plots of deformation Vs. Time for each of the load increments are shown in Figure 28 through Figure 31 Figure 28 Results of 1-D Consolidation Test for Confining Pressure = 0.25tsf 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (0.25tsf)

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69 Figure 29 Results of 1-D Consolidation Test for Confining Pressure = 0.5tsf Figure 30 Results of 1-D Consolidation Test for Confining Pressure = 1.0tsf Based on the above plots, the values for time and deformation for each load increment corresponding to 50% and 100% consolidation using the graphical method (see interpretation on plots) are shown in Table 6 0.09 0.10 0.10 0.11 0.11 0.12 0.12 0.13 0.13 0.14 0.14 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (0.5 tsf) 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (1.0 tsf)

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70 Figure 31 Results of 1-D Consolidation Test for Confining Pressure = 0.25tsf Table 6 Summary of Results from 1-D Consolidation Tests Percent Consolidation Property Load = 0.25tsf Load = 0.5 tsf Load = 1.0tsf Load = 2.0tsf 50% Time (min) 55 20 15 15 Deformation (in) 0.050 0.021 0.008 0.003 100% Time (min) 105 100 95 45 Deformation (in) 0.065 0.047 0.014 0.005 From the consolidation data presented above the compression index of the kaolin sample was estimated based on the void ratio computed at the end of each load increment test computed based on the following formula (Das, 2007): Void ratio before test: Void ratio after test: 0.001 0.002 0.003 0.004 0.005 0.006 0.007 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (2.0 tsf)

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71 and: where: = Initial Height of Specimen (in) = Final Height of Specimen (in) = Height of Specimen Solids (in) = Mass of Specimen (lbs) = Cross Sectional Area of Specimen (in ) = Specific Gravity of Specimen Solids = Unit Weight of Water (lbs/in ) A plot showing the final void ratios after each load test along with a linear interpretation of the change in void ratio Vs. change in pressure is shown in Figure 32 Figure 32 Interpretation of Re sults from 1-D Consolidation Tests y = 0.086x + 0.785 0.600 0.620 0.640 0.660 0.680 0.700 0.720 0.740 0.760 0.780 0.800 0.11Void RatioPressure (tsf)1 D Consolidation Test Void Ratio Vs. Log Pressure

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72 Based on this analysis a compression index for the Kaolin sample was computed based on the following calculation (Das, 2007): 6.3 Modified Ring Shear (Adhesion) Test The Bromhead ring shear device utilized for th e adhesion testing is not equipped with data acquisition systems. Due to this, observations of vertical displacement and proving ring displacements were collected visually and copi ed onto lab testing sheets similar to the electronic ones presented in Appendix D For much of the testing a video recording device was set up on a tripod over one of the provin g rings. After the test was complete the tape would be reviewed for observations of proving ring displacement. A screen shot from one of the video files recorded is shown in Figure 33 Figure 33 Screenshot of Proving Ring Displacement Gage from Video Recording Device For this laboratory program, 19 separate consolidated undrained ring shear adhesion tests were conducted between October 25th 2013 and February 20th 2014. Sixteen of these tests

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73 were normally consolidated samples, half of wh ich were tested with the top steel ring that had a roughness coefficient of 2m and the other half with the top steel ring that had a roughness coefficient of 20m. Confining pressures of 0.25tsf (3.47psi), 0.5tsf (6.94psi), 1.0tsf (13.89psi), and 2.0tsf (27.78psi) were used to conduct the test. For each confining pressure two consolidated undrained tests were conducted for each steel ring. The other three tests conducted were overconsolidated un drained tests with overconsolidation ratios (OCR) of two, four and eight. The author decided before the laboratory progra m began that the peak shear stress as well as the residual shear stress should be determined for each of the tests. This meant that a new sample of clay had to be prepared, molded in to the chamber, consolidated, shear tested and the chamber disassembled and completely clea ned for every shear test conducted. This proved to be a very time consuming process and due to the time required to achieve 95% consolidation (or final swelling), typically only a few normally consolidated tests or only one over consolidated test could be conducted within a weeks timeframe. Initially, the laboratory program was scheduled to begin in September 2013 but the first few tests attempted were failures. The author only planned on replacing the top brass ring that comes with the Bromhead ring shear device wi th the low carbon steel rings machined to different roughness coefficients. For these initially tests the lower brass ring, which has a much larger roughness coefficient, was used in the test. The brass rings that were shipped with the device are porous (Wykeham Farrance, 1979), most likely to aid in the dissipation of pore water pressures during consolidation and drained shearing test for which the device is most widely used. The adhesive suction forces that are developed when an interface

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74 adhesion test is conducted between clay and a nother material are greatly reduced when the clay is in contact with a porous material. As a re sult, all of these initially samples failed not at the interface with machined steel rings or within the clay sample themselves. The samples instead failed at the interface with the bottom br ass, porous ring instead. In fact the samples maintained the ring chamber shape when the top loading platen was lifted from the bottom platen. These failed tests indicated the exis tence of the suction force and demonstrated that the force has a significant impact on the adhe sive shear as well as cohesive strength of a clay specimen. In order to determine the normal and shear forces from a ring shear test using the Bromhead ring shear apparatus the following equations, from the manual provided in Appendix A are used (Wykeham Farrance, 1979): Since the sample is narrow in comparison to the diameter the approximation is appropriate. The torque transmitted through the sample is given by: Since the torque is given by mean load on the proving rings the shear stress is given by: The normal effective stress is given by: Where: P = Total Load (10x the hanger load)

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75 R1 = Inner ring radius R2 = Outer ring radius F1=Force on ring 1 L=Distance between proving rings The above calculations are built into the spreadsheets that contain the ring shear adhesion testing data presented in Appendix D. All of the samples tested failed at or near the interface with the top steel ring, based on visual observation. The determination of the interface shear strength parameters from the testing data was performed similar to the mohrcolumb shear strength parameters. In this way an interface friction angle and an adhesive (tensile) force was estimated from the test results. The interface friction angle is the slope of the normal stress Vs. Shear stress line and can be determined from the following equation in keeping with the Mohr-Columb theory: The adhesive force is determined from the ex trapolation of the norma l Vs. shear stress line to the intercept with the Y or zero normal force axis (Mohr-Coulumb type material). The following sections present the results of the interface shear testing based on the variables considered in the laboratory tests. 6.3.1 Interface Shear Test For the normally consolidated samples the results of the interface shear tests are presented in graphical form in Figure 34 and summarized in Table 7 for the tests with the ring of roughness 2m and Figure 35 and summarized in Table 8 for the tests with the ring roughness of 20m.

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76 Figure 34 Results of Normally Consolid ated Ring Shear Interface Tests for Top Ring = 2m Table 7 Summary of Results of Normally Consolidated Ring Shear Interface Tests for Top Ring = 2m Date Tested (Appendix X) Normal Stress (psi)p Peak Shear Stress (psi)r Residual Shear Stress (psi) 12/13/2013 3.47 1.57 0.76 12/13/2013 3.47 1.19 0.45 10/25/2013 6.94 3.05 2.68 12/13/2013 6.94 3.42 3.15 10/28/2013 13.89 5.54 5.13 11/1/2013 13.89 4.98 3.62 10/30/2013 27.78 9.34 7.36 12/2/2013 27.78 8.14 6.97 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.0000.1000.2000.3000.4000.5000.600Shear Stress (tsf)Displacement (in)Results with Top Ring R = 2m 3.47 3.47 6.94 6.94 13.89 13.89 27.78 27.78 Confining Pressure

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77 Figure 35 Results of Normally Consolid ated Ring Shear Interface Tests for Top Ring = 20m Table 8 Summary of Results of Normally Consolidated Ring Sh ear Interface Tests for Top Ring = 20m Date Tested (Appendix X) Normal Stress (psi)p Peak Shear Stress (psi)r Residual Shear Stress (psi) 11/6/2013 3.47 1.93 0.26 11/16/2013 3.47 1.05 0.78 11/15/2013 6.94 4.10 2.28 11/19/2013 6.94 3.70 3.19 11/8/2013 13.89 7.62 6.25 11/20/2013 13.89 6.02 5.14 11/6/2013 27.78 9.72 8.39 11/22/2013 27.78 9.39 8.27 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.0000.1000.2000.3000.4000.5000.600Shear Stress (tsf)Displacement (in)Results with Top Ring R = 20m 3.47 3.47 6.94 6.94 13.89 13.89 27.78 27.78 Confining

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78 There is apparently some scatter in the observations for some of the tests, likely due to knocking created by the machines motor system, buildup of frictional forces along the outside edge of the sample or possibly local inconsistencies with the ring sample due to the placement process. Generally the curves of Displacement Vs. Shear Stress show a peak stress value at very low displacements followed by a drop, followed by a leveling off as the shear surface approaches residual values. Th e peak value seems to occur at larger displacements for the 2tsf (27.78psi) confining pressure than for the other, lower confining pressure tests. In actuality the location of th e peak shear stress value likely occurs at locations further down the displacement curv e for increasing confining pressures but the difference between these locations were too subt le to observe without a data acquisition system. Comparing the testing observations of the repeat tests in Figures 34 and 35 indicates good agreement which indicates repeatability in the testing results. 6.3.2 Effect of Ring Surface Roughness As mentioned previously the two steel rings that were utilized as top (interface-shear) rings in the tests were made of low carbon structura l steel and were machined to have specific roughness coefficients along a profile following the center of the ring rotationally. The first ring was finished to roughness coefficient of approximately 2m (0.002mm) and is smooth to the touch. The second ring was finished to a roughness coefficient of approximately 20m and has a slightly rough feel when rubbing with fingertips. The difference in the ring roughness is otherwise difficult to discern except for the slightly different glean of each ring under a strong light ( Figure 27 ). A comparison of one of the characteristic rotational displacement Vs. shear stress plots for each of the confining pressures tested and with each of the top rings is shown in Figure 36

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79 Figure 36 Comparison of Results of Norma lly Consolidated Ring Shear Interface Tests for Top Ring = 2 m & 20m At the lower confining pressures of 0.25tsf (3.47psi) and 0.5tsf (6.94psi) there appears to be little divergence of the peak and residual shear stresses observed in the samples sheared against the ring with surficial roughness of 2m and that of 20m. Comparison of the results taken from the higher confining pressures, however, indicates a relatively large divergence in which the interface shear stress of the samples in contact with the ring with surficial roughness of 20m were about 10-20% larger for peak and 10-15% larger for residual than the shear stresses for the sample in contact with lower surficial roughness ring. Comparison of the results from the confining pressures of 1.0tsf (13.89psi) and 2.0tsf (27.78psi) demonstrate approximately the same di vergence between the two rings. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0.000.100.200.300.400.500.60Shear Stress (tsf)Displacement (in)Results with Top Ring R = 2m & 20m 3.47 6.94 13.89 27.78 3.47 6.94 13.89 27.78 R = 2m R = 20m

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80 6.3.3 Effect of Over Consolidation In addition to the interface ring shear tests conducted on normally consolidated samples several tests were conducted on over consolidated samples utilizing the ring with the surficial roughness coefficient of 20m. Observations r ecorded from the tests are presented on the observation logs in Appendix E A summary of the peak and re sidual shear stresses for each of the over consolidation ratios is shown in Table 9 A plot of the rotational displacement Vs. interface shear stress is presented in Figure 37 Table 9 Summary of Results for Over ly Consolidated Ring Shear Tests Date Tested (Appendix X) OCR Over consolidation Ratio Normal Stress (psi) p Peak Shear Stress (psi) r Residual Shear Stress (psi) 11/22/2013 1 27.78 9.39 8.27 2/13/2014 2 13.89 10.36 8.15 2/20/2014 4 6.94 11.17 7.93 2/7/2014 8 3.47 11.98 8.67 The table and plots indicated increasing peak interface shear strength with increasing Over Consolidation Ratio (OCR) despite the fact that these samples were tested under lower confining pressures. In fact the peak shear stre ss measured in the tests increased by 10%, 19% and 28% over the normally consolidated sa mple for OCRs of 2, 4 and 8 respectively. The residual strengths however appear to be approaching the same value consistent with a maximum confining pressure of 2tsf (27.78psi). The plot also indicates that the displacement

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81 at which the peak shear stress is measured is less for the samples that are more heavily over consolidated. 0 2 4 6 8 10 12 0.000.100.200.300.400.500.600.70Shear Stress (tsf)Displacement (in)Results with Top Ring R = 20m OCR=1 OCR=2 OCR=4 OCR=8

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82 Figure 37 Results of Ov erly Consolidated Tests 6.3.4 Consolidation During Shear Testing The observations taken from the vertical displacement gage are shown on the lab observation testing sheets in Appendix D and Appendix E respectively Plots of the rotational displacement Vs. vertical displacemen t (consolidation) for each of the normally consolidated samples tested are presented in Figure 38 for the samples tested with a ring roughness of 2m and Figure 39 for the samples tested with a ring roughness of 20m. 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 0.000.100.200.300.400.500.600.70Shear Stress (tsf)Displacement (in)Results with Top Ring R = 20m OCR=1 OCR=2 OCR=4 OCR=8

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83 Figure 38 Consolidation of Samples during Ring Shear for Top Ring = 2m Figure 39 Consolidation of Samples during Ring Shear for Top Ring = 20m 0.00 0.01 0.01 0.02 0.02 0.000.100.200.300.400.500.60Vertical Displacement (in)Displacement (in)Consolidation with Top Ring R = 2m 3.47 3.47 6.94 6.94 13.89 13.89 27.78 27.78 0.00 0.01 0.01 0.02 0.02 0.000.100.200.300.400.500.60Vertical Displacement (in)Displacement (in)Consolidation with Top Ring R = 20m 3.47 3.47 6.94 6.94 13.89 13.89 27.78 27.78

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84 All of the samples tested consolidated during shear testing and in general followed the same pattern in the rotational displacement Vs. Vertic al displacement plot. Initially the samples consolidated at a faster rate which tended to level off as the samples approached residual shear conditions. Repeat tests show similar re sults in terms of consolidation during shear indicating good repeatability of the results. There appears to be some reverse correlation between the total amount of consolidation ex perienced by the samples and the confining pressure which the samples were subject to but this relationship does not always exist. Plots of the rotational displacement Vs. vertical displacement (consolidation) for each of the overly consolidated samples (and the normally consolidated comparison sample) tested are presented in Figure 40. Figure 40 Vertical Displacement of Overly Consolidated Samples 0.008 0.006 0.004 0.002 0 0.002 0.004 0.006 0.008 0.01 0.012 0.000.100.200.300.400.500.60Vertical Displacement (in)Displacement (in)Results with Top Ring R = 20m OCR=1 OCR=2 OCR=4 OCR=8

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85 The plot indicates the largest dilation followed by the largest rate and maximum value of consolidation was observed in the sample init ially consolidated at a pressure of 2tsf (27.78psi) and tested at a confining pressure of 1tsf (13.89psi) with a corresponding OCR equal to one. The sample with the next highest OCR of two showed a similar but much more subdued pattern. The sample with the highest OCR equal to 8 that was initially consolidated at a pressure of 2tsf (27.78psi) an d then tested at a confining pressure of 0.25tsf (3.47psi) demonstrated almost no change in ve rtical displacement over the interface shear testing interval.

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86 6.3.5 Interface Shear Strength As discussed in Section 2.3.3, the interfacial sh ear strength between clay and a solid material surface can be presented in terms of a Mohr-Coulomb failure type envelope. Plots of the average Normal Stress Vs. Interface Shear Stre ss for each of the confining pressures are shown in Figure 41 for the top ring with a roughness of 2m and Figure 42 for the top ring with a roughness of 20m. Interpretations of a bi-linear Mohr-Coulomb failure envelope are shown on the plots for both the peak and residual strengths. Figure 41 Normal Vs. Shear Stress Te st Results for Top Ring Roughness = 2m 0.0 2.0 4.0 6.0 8.0 10.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Ring R =2m Peak Residual Peak 1 Peak 2 Residual 1 Residual 2

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87 Figure 42 Normal Vs. Shear Stress Te st Results for Top Ring Roughness = 20m A summary of the interface friction angle an d interface adhesion force for the normally consolidated samples tested with the top ring with a roughness of 2m is presented in Table 10 and with the top ring with a roughness of 20m is presented in Table 11 Table 10 Interface Shear Strength be tween Kaolin and Top Steel Ring with Roughness = 2m Strength Envelope Friction Angle (degrees) A dhesive Force (psi) Adhesive Force (kPa) Peak 1 22.9 0.17 1.17 Residual 1 22.0 0.36 2.48 Peak 2 12.0 2.75 19.0 Residual 2 7.8 3.34 23.0 Table 11 Interface Shear Strength betw een Kaolin and Top Steel Ring with Roughness = 20m Strength Envelope Friction Angle (degrees) Adhesive Force (psi) Adhesive Force (kPa) Peak 1 26.8 0.25 1.7 Residual 1 24.5 0.64 4.41 0.0 2.0 4.0 6.0 8.0 10.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Ring R=20m Peak Residual

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88 Peak 2 12.0 3.80 26.2 Residual 2 10.7 3.07 21.2 A comparison of the two sets of curv es for peak strengths is shown on Figure 43 and for residual strengths on Figure 44 Figure 43 Normal Vs. Shear Stres s Test Results, Peak Strengths Figure 44 Normal Vs. Shear Stress Test Results, Residual Strengths From the plots, it is obvious that the streng th envelopes for the interface shear strength between the clay and the ring with a roughness of 20m is larg er for both peak and residual 0.0 2.0 4.0 6.0 8.0 10.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Peak 5um 20um 0.0 2.0 4.0 6.0 8.0 10.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Residual 5um 20um

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89 strengths. The first portion of the bi-linear strength envelopes demonstrated very small negative adhesive resistance to shear and most of the shear strength mobilized is due to frictional forces. The relative divergence of th ese curves becomes more apparent at higher confining pressure which is the second part of the bi-linear strength envelope. For the peak strengths the friction angles for this portion of the envelope are identical and the difference between the location of the lines is the addi tional adhesive resistance (difference = 1.05psi) generated by the ring with the larger roughne ss coefficient. For the residual strengths the adhesive force for the ring with the smalle r roughness coefficient generated the larger adhesive resistance (difference = 0.27psi), bu t the difference is nominal compared to the values of the respective adhesive strengths. The location of the normal and shear stress measurements for peak and residual strengths of the overly consolidated clay samples is shown on Figure 45 and Figure 46 respectively. Figure 45 Location of Overly Consolid ated Peak Strength Tests Relative to Normally Consolidated Strength Envelo pe for Top Ring Roughness = 20m 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Ring R=20m Peak 20m Peak OCR=8 OCR=4 OCR=2 OCR=1

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90 Figure 46 Location of Overly Consolid ated Residual Strength Tests Relative to Normally Consolidated Strength Envelo pe for Top Ring Roughness = 20m From the plots it is obvious that the overly c onsolidated test results plot above the envelope for the normally consolidated strengths. The increa se becomes greater at larger ratios of over consolidation which also corresponds to lower normal stresses. 6.3.6 Moisture Content Measurements The moisture content of the samples was measured both before and after each ring shear test. A summary of the moisture content testing for the normally consolidated samples is presented in Table 12. A summary of the moisture content testing for the overly consolidated samples is presented in Table 13 It is apparent from the results that all of the samples were initially prepared at moisture contents above the moisture content that re mained after consolidation. The summary of results indicate that for the normally consolidated samples increasing the confining pressure reduces the moisture content of the samples for the test. This is a predictable result in which 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 051015202530Shear Stress (psi)Normal Stress (psi)Normal Vs. Shear Stress, Ring R=20m Residual 20m Resid OCR=8 OCR=4 OCR=2 OCR=1

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91 the water is being squeezed out of the pore spac e, similar to what was observed during the 1D consolidation test (Section 6.2) Table 12 Moisture Contents Before and Af ter Normally Consolidated Shear Testing Confining Pressure (psi) Moisture Contents (%) Before Test After Test Ave After Test Range 3.47 72.5 63.1 54.3 75.7 6.94 72.5 60.4 55.3 67.6 13.89 71.0 58.0 51.5 67.8 27.78 71.3 43.0 40.3 44.6 Table 13 Moisture Contents Before a nd After Overly Consolidated Shear Testing Over Consolidation Ratio Confining Pressure (psi) Moisture Contents (%) Before Test After Test 1 27.78 70.0 40.3 2 13.89 70.9 41.0 3 6.94 71.2 45.5 4 3.47 71.9 48.6 For the overly consolidated samples the moisture content of the samples measured after the tests appear to increase in comparison to the base case sample tested at and OCR equal to one (normally consolidated). The increases are incremental in comparison to the decrease in moisture content that was observed from the normally consolidated tests.

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92 7 Summary and Conclusions The use of the tunnel boring machine as a means of mechanically excavating through soils to build linear underground projects is growing in the US and throughout the world. The ability of certain clay minerals to adhere or st ick to the metal components of a TBM in the presence of water has the potential to have measurable implications on the schedule and budget of a particular project. Shearing of a clay in contact with a metal surfa ce can occur in one of th ree ways; at the claymetal contact, within the clay structure or as a combination of the two. Similar to shearing strength at clay-clay contact the adhesive shearing strength of clay-metal is dependent on the normal force applied to the failure plane. If the (cohesive) shear strength of the clay is larger than the interfacial (adhesive) shear strength of the clay-steel contact than the clay will shear at the contact with the steel and sticking will not occur. If however the interfacial shear strength is higher than sticking, and potentially buildup of clay material, will occur. It has been shown from previous studies and the one conducted for this report, using the ring shear or torsion device, that the adhesive strength of clays to other surfaces can be described in terms of the Mohr-Columb failu re criteria. Similar to the shear strength parameters for the clay of friction angle and co hesion, the adhesive shear strength of clay can be defined in terms of the adhesive friction angle and adhesive tensile force. The adhesive tensile force is attributed entirely to the suction pressure developed at the claymetal interface and can be measure independentl y from the contact friction angle. Adhesive friction angle is attributed to the penetration of the clay particles into the asperities of the

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93 metal surface and the resulting force of redistribu tion during shear. In this way as the microroughness of the steel surface, ie. the real contac t area, increases so will the adhesive friction angle. The previous chapters of this report deal prim arily with the physical and chemical processes of clay-steel adherence and how the variation of certain parameters ma y affect the relative magnitude of the phenomena. Clay mineralogy is the primary contributing factor for adhesion to metal surfaces and the main indicato r of susceptibility. The ability of swelling (ie. sticky) clay minerals to attract and absorb water molecules into their lattice structures creates the suction force at the clay-metal contact. The potential for attraction of positively charged water molecules to the negatively charged surfaces of clay minerals increases with increased surface area of the clay particle s. As a result the more scalelike clay particles that have very large surface areas per unit weight will have a higher likelihood of sticking to steel parts. The activity of a clay is measure of the intensi ty of the surface charge and can be inferred using basic laboratory testing techniques. Other more complex methods for determining the swelling potential of clays include measuring the cation exchange capacity or using x-ray diffraction to identify clay mineral types. The behaviors of adhesion and cohesion in colloids (particles < 0.1 m in diameter) is also a function of the water content and a clay would have to have a water content in its plastic range for sticking to occur. Relative consisten cy is a measure of the in-situ water content of clay within its plastic range relative to its plasticity index. A maximum value of adhesive tensile strength will occur at a moisture c ontent corresponding to a relative consistency between zero and unity where the suction pressur es are at their highest. Increasing the

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94 moisture content beyond this point will cause a drop in suction force as more free water is available for bonding. Below the water table th e consistency of clay is typically dependent on the level of consolidation of the soil. Under high consolidation pressures the plate like clay particles will tend to align in sheets norma l to the maximum pressure. If high contact pressures were to form between clay and a meta l surface then the real contact area would increase as the clay particles aligned. 7.1 Ring Shear Device Interface Testing The modified ring shear apparatus used for the primary data collection for this study is a relatively simple apparatus to create, provided a ring shear device similar to the Bromhead type is accessible. To condu ct the test both the top and bo ttom rings will need to be replaced with the stainless steel or an equi valent non-porous material of the same size and shape. Otherwise a clay with any magnitude of adhering potential will stick to the nonporous material and shear at the interface with the porous material. The ring shear device is well suited to this type of testing because of the relatively even distribution of shearing strains during the application of the rotational shear forces. The rings used for this study are comparable to the interface materials used in previous studies in which shearing was observed both at the interface of clay and steel and below the interface within the clay itself. The surficial roughness of the rings machined specifically for this testing are comparable with roughnesss for construction materials used in the soft ground tunneling and within other related geo-civil industries. The Kaolin clay used for the interface testing is composed of stacked gibbsite and silica sheets in a one to one fashion. The Cation Ex change Capacity of the clay sample is 9,

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95 according to the distributor, which places it in the center of the range for Kaolin clays according to data from Grim (1962) Kerr (1951) Lambe & Whitman (1969) and Mitchell (1976). Previous studies indicate the clay sample would be at the lower end of the distribution of potential adherence strength for sticky clays but, since both Illite and Montmorillonite clays are less abundant in nature the clay sample used for the testing is considered to be a good representative for potentially sticky or clo gging materials in TBM applications. The focus of the testing program was on the un drained shear or quick shear of normally and overly consolidated, saturated clay specimens since that is most representative of the scenario encountered in the field when TBM clogging issues occur. The atterberg limits estimated from the testing indicate that the kaolin sample exhibits fairly typical properties for clay of moderate activity. The average moisture contents of the samples measured after the tests were complete are presented in Table 14 in terms of the consistency index. Table 14 Consistency Index of Clay Samples Tested Normal Stress (tsf) OCR Peak Shear Stress (psi) Residual Shear Stress (psi) Average M.C. (%) Ic 0.25 1 1.5 0.5 63.1% 0.17 0.5 1 3.0 2.7 60.4% 0.09 1 1 6.8 5.7 58.0% 0.01 2 1 9.4 8.3 43.0% 0.45 1 2 10.4 8.2 41.0% 0.52 0.5 4 11.2 7.9 45.5% 0.38 0.25 8 12.0 8.7 48.6% 0.28

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96 For comparison the consistency of the sticky index is estimated to be about 0.7. All of the samples associated with the test results presented in this report appeared to have sheared at or near the contact with the top, low carbon st ainless steel ring., which indicates that the cohesive shear strength within clay samples wa s higher than the adhesive interfacial shear strength. All of the shear stress Vs. displacement plots ( Figures 34, 35 & 37) displayed a similar shape of rapid increase in shear strength up to a peak values, followed by a decrease in shear strength with decreasing slopes approaching re sidual values. For a TBM excavation scenario this means that the highest shear resistance at the interface with the cutting tools will occur right at the start of cutter head rotation. The commonly observed occurrence of clay materials forming a cake on the fr ont of the TBM excavation face ( Figure 3) means that the peak adhesive strength of the clays has not b een overcome by the ro tational force of the cutter head or the cohesive strength at the clay to clay contacts. For overly consolidated clay samples the peak strength of the clay increa ses compared to normally consolidated clays, making adhesion more difficult to overcome. A kaolin clay sample was tested with two separa te steel rings with different surficial rough nesses. The finish of the surface of the rings chosen to be similar to a TBM cutter head and tooling at the start of tunneling operation and at some point during the tunnel drive when the tools have been subject to a certain level of abrasion on the micro scale. The roughness of the ring with more asperities could also represent the surficial roughness of new or refurbished equipment depending on the c ontractors requirements and manufacturers specifications. From the ring shear test results it is clear that both the peak and residual

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97 strengths mobilized was about 10-20% higher for the ring with the larger roughness coefficient, but only when the confining pressure exceeded 1tsf (13.89psi). The increase in interface shear resistance is likely due to a combination of an increase in frictional adhesive force caused by the larger confining pressure an d an increase in adhesive (tensile) force due to the decreased moisture content of the sample under the larger confining load. The normal pressures chosen for the testing were similar to stresses used in other similar type tests and also were chosen to be indicative of pressures likely to be encountered in a pressurized face TBM excavation chamber (Zimnick 2000). It was determined that highly overly consolidated clay samples exhibited peak interfacial shear strengths as much as 10 to 30% more than normally consolidated samples at the same confining pressures. This trend may continue as OCRs values are increased since a threshold value was not reached in the adhesion tests. Exceedance of peak stress, however, occurred at lower rotational displacements than for the normally consolidat ed samples indicating a more brittle, as opposed to plastic, type failure mechanism. From the plots it appears that while the nor mally consolidated samples have a trend of consolidation over displacement, the over c onsolidated samples initially dilate which is followed by consolidation as they approach re sidual strengths. The normally consolidated samples all experienced additional consolidation during interfacial shear. The overly consolidated samples on the other hand, dilated during the initial stages of shearing. The largest magnitude of dilation occurred at lower values of over consolidation. At higher OCRs very little consolidation occurred during shearing. In the field the increase in volume of clay materials during shearing may furthe r exacerbate the potential for TBM clogging.

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98 The results as they have been presented in th e plots in Section 6 illustrate one of the primary focuses of the testing program. As surficial roughness of shinny-smooth, steel equipment such as brand new cutting gear or a TBM fa ce plate on a TBM cutterhead, increases in roughness by approximately one order of magnitude the interfacial shear resistance between the metal and a sticky clay formation or clum ps of clay from the formation increases as well. Based on relative comparisons it appear s that after some threshold of confining pressure is reached the level of increase in shear resistance remains about the same. 7.2 Comparison of Results from Previous Studies Atterberg defined the adhesion limit in addi tion to the more commonly used plastic and liquid limits. The adhesion limit is the moisture content at which clay-metal sticking begins to occur. In this study the adhesive limit for the Kaolin clay sample utilized has been estimated to be about 35%. The range of moistu re content at which clay will adhere to metal was later termed the Rieke index, which was esti mated to be a range in moisture content of about 22% assuming the clay no longer adhe res to metal beyond its liquid limit. A comparison of the sample used for the ring sh ear interface testing with other samples used for interface testing referenced throughout this report is shown in Figure 47

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99 Figure 47 Comparison of Clay Samples from Various Studies Tests conducted for the purpose of determinin g the adhesive tensile force and adhesive friction angle were performed by Bowden an d Taylor as far back as the 1950s. In 1979 Thewes (Section 3.2) developed a testing appara tus to focus on the adhesive tensile strength of clays in contact with steel. He tested samp les from six different clayey formations and determined that clay mineralogy and consis tency were the primary indicators of TBM clogging potential. He also gathered information from several tunnel construction projects with varying levels of clogging issues to develop a chart for assessing the clogging potential. His observations and recommendations regardin g clay consistency and the atterberg limits provide a basis for indicating the likelihood of experiencing potential clogging issues in the other adhesion studies described in this report. The Thewes (2005) chart indicates a likelihood for adherence based on a clays plasticity index. This observed correlation is probably beca use the plasticity index correlates well with Kooistra, Sepiolite (Bentonite) Tokarz

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100 the activity level and the likely presence of swe lling clay minerals. Comparison of this chart with the results from other studies and the one done for this report using the ring shear apparatus, indicate that the recommendations do not exactly conform to the testing results for adhesive strengths mobilized in drained and undrained clay samples in which higher adhesive (tensile) resistance strengths were obs erved at consistency indices between 0.4 and 0.6 (Spagnoli, 2000) and higher adhesive sh ear resistance strengths were observed at even lower indices (this report). Littleton modified a standard shear box to determine the adhesive shear strength parameters between clay and a smooth low carbon structura l steel. The steel surface was polished to a roughness of about 0.2 m and the clays included a normally consolidated (S1) and an overconsolidated (S2) high plasticity clay. Adhesive shear strength results were compared with results from classical shear box tests. Results from Littletons undrained tests at a confining pressure of 360N are summarized in graphical form in Figure 48

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101 Figure 48 Comparison of Test Results for Consolidated Drained Modified Direct Shear Tests Conducted by Littleton From the summary plot the over consolidated sample sheared against the metal surface rather quickly after initiation compared to the normally consolidated sample. This is similar to the results for the ring shear adhesion test fo r the overconsolidated samples, presented in Section 6.3.3. After shearing the over consolid ated sample displayed a strain softening behavior which is likely the result of dilation an d the redistribution of the clay particles. The slightly higher adhesive strength of the nor mally consolidated sample used by Littleton is attributed to the higher plasticity index which indicates either a higher fines content or a greater abundance of swelling clay minerals. For both samples the initial work done to overcome the adhesive strength of the sample was greater than the work needed to overcome the cohesive strength of the sample This would indicate sticking potential and subsequent build-up of material on metal tools in a TBM excavation scenario. Also from Littletons results the higher the confining pre ssure the more work is needed to shear along

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102 the clay-steel contact. The same results were observed in the ring shear adhesion tests for confining pressures up to 2tsf (27.8psi). The results indicate that the adherence of clay to metal surfaces is more dependent on the peak adhesive strength of the clay-metal contact than the residual. After initial shearing the residual adhesive shear strength was less than the internal shear strength for both samples used by Littleton which is also true of the sample used in the ring shear test. Several working groups working out of the University of Delft (Zimnik and Kooistra) applied the techniques used by Littleton with the use of a similar modified shear box apparatus to the conditions of clay-metal interface in a TBM excavation. Consolidated undrained tests were conducted on normally c onsolidated and over consolidated clay samples with shearing at various confining pressures and across steel plates of varying surficial roughness. The results from these interfa ce shear tests were similar to the results of the interface ring shear tests. Results for undr ained tests for previous studies and this study are summarized in Figure 49 for comparison.

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103 Figure 49 Summary of Results from Vari ous Authors for Consolidated Drained Modified Direct Shear Tests The curves from the previous tests indicate that a bi-linear normal Vs. shear stress relationship exists for overly consolidated samp les, but it was observed to also occur from normally consolidated clay reconstituted from powder for the ring shear interface test. Based on the previous studies, it was determined that adhesive shear strength increases linearly with increasing confining pressure up to 500kPa (72 .5psi) indicating that th is trend is likely to continue beyond the normal stresses used for this study. Based on a compilation of test results by Zimnik (2000) a slight increase in adhesive shear strength was observed particularly with an increasing roughness between 2.4 and 4.7 m. Increased steel to clay contact time led to an in crease in adhesive shear strength, particularly at higher confining pressures. A similar result was observed utilizing the two diffe rent rings used in the testing for the ring shear apparatus for this study. An increase of 10-20% in peak shear strengths was estimated

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104 for increasing the roughness coefficient be tween the rings with surficial roughness coefficients of 2m and 20m. The increased adhesive shear strength due to increased micro-roughness became larger with the higher confining pressures. Yoshimi performed ring shear adhesion tests on several sands utilizing rings machined to have different roughnesss. The difference in sh earing strain was estimated from measuring the movement embedded led markers within the sample. The maximum variation of shear strain across the sample was determined to be less than ten percent. The test indicated the benefit of using the ring shear device as oppos ed to the more common direct shear device. He determined that the coefficient of mobiliz ed friction between the sand and steel surface was the same for all surfaces prior to initial shear. After shearing the difference in the coefficient of friction was highly dependent on the steel roughness up to a roughness coefficient equal to the mean grain size abov e which there was little increase. The peak and residual friction coefficients were a bout equal for steel roughnesses above 20 m (10% of the mean grain size). This critical value of sur ficial roughness corresponded to the roughness at which the samples began to dilate during shearing. In an effort to add to the growing body of know ledge in regards to clays adhering to TBMs a testing program utilizing a ring or torsion shea r testing apparatus was conducted as part of this study. One of the objectives of the program was to acquire results from a different type of test to compare with the adhesive shea r strength of clays tested previously under consolidated undrained conditions using the direct shear apparatus. The results of all of the testing indicate the material parameters which are most critical for sticking potential and should be evaluated in an order close to the following:

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105 1. Clay Mineralogy Includes the abundance of swelling (absorbing) clay minerals and is also measured by the activity of a clay Can be estimated based on simple Atterberg limit testing. 2. Moisture Content Availability of free wa ter and level of saturation of a clay formation. For a clay to be potentially adhering the moisture content must exceed the sticky limit. If the clay is soft and oversaturated beyond its liquid limit than the sticking potential reduces to values observed below this sticking limit. 3. Consistency & Consolidation Includes the normal (overburden) stresses currently being applied to a clay formation relative to the history of normal stresses applied to the geology. The most recent information in dicates that relative consistency indices of 0.4 to 0.7 result in the highest level of clay-steel adherence. Additionally larger values of over consolidation will result in higher adhesive strengths as long as the moisture content (available water) is not too low. 4. Steel Roughness Micro-roughness exceeding 2m (0.002mm) should be evaluated for their effect (increase) on interfacial shear strength. The comparison of the results using the di fferent apparatus for normal stress versus measured sheared stress for the interface of th e steel and clay is presented here only to indicate good agreement in the trend of the en velopes. Due to the differences in testing procedures, equipment and the complex distribution of stresses with the direct shear samples careful consideration should be app lied before drawing conclusions from these comparisons. Only after increased numbers of clay-steel adhesion tests have been performed

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106 using different materials under various conditi ons should the results of the two different methods be compared. 7.3 Implications for TBM Cu tter head & Excavation Soft ground tunneling projects present a seemin gly infinite number of technical difficulties for the engineer and the contractor. Most of the difficulties are due to the ground conditions that are encountered within a tunnel drive. Today the use of Earth Pressure Balance and Slurry TBMs is common in underground constr uction projects. Each of these machines and a variety of hybrid types are designed to match the geologic conditions and meet the technical requirements of their intended drive. Clogging of EPB and slurry TBMs is a co mmon problem, particularly in some urban locations underlain by problematic geologic form ations where tunneling is more prevalent. Clogging issues typically begin at the excava tion face but issues can also develop at the suction inlet area, within the working chamber, in the screw conveyor and anywhere in the mucking system. Once adhesion initiates, cohesive forces cause the buildup of material and, in the case of the cutter head, contact pressur es will increase further progressing the issue. On the cutter head adhesion will typically begi n at the center where th e rotational speed is less. The size of a TBM and the cutter he ad is typically a function of the project requirements. Just like the machines themselves the cutter head of a TBM can be designed in a multitude of different ways to meet the anticipated ground conditions. The actual forces experienced at the conta ct of the steel cutter head and the geologic formation or portions of the fo rmation as they are pulled away from the excavation heading

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107 are complex and the determination of these forces is beyond the scope of this report. At the most basic level at the local scale the adhesi ve force of a clay and a steel surface and by comparison the occurrence of clay sticking to a steel cutter head surface can be broken down in terms of a normal force and a shear force. At the global scale the forces imparted to the excavation face by a TBM include a contact pr essure from the TBM thrust mechanisms and a shear force caused by the rotation of the cutter head by the motor. Test results and observations related to interfacial shear strength indicate that an understanding of a clay formations mineralogica l and consolidation properties, as well as the previous loading history of the formation, are key to determining the potential for adhering or clogging of a TBM during construction. At this point, without an understanding of the complex distribution of shear and normal forces at the cutterhead (for which each TBM design is unique) we can only summarize the parameters that are likely to result in larger magnitudes of adherence and therefore and in creased likelihood of clogging. To summarize those properties from the current and previous st udies the presence of swelling clay minerals and consistency indices between 0.3 and 0.7 ar e likely to have the highest potential for sticking. Additionally over consolidated clays w ill have a larger peak adhering strength and will tend to dilate during shearing which coul d further exacerbate clogging issues in the working chamber and muck conveyance system. The results also indicate there are measures that can be taken during construction which will most likely reduce the potential for adherence and clogging. It has been found that the highest rates of advance have been achieved by applying the optimal combination of thrust and cutter head torque. Lowering the driving for ce applied by the thrust cylinders will reduce

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108 the contact pressures on the face as will lowering the fluid or air pressures in the case of a supported face, which will reduce the peak and resi dual shear strengths of the clay material. The addition of water to the excavation face ma y not reduce the likelihood of sticking and may actually increase it, but case studies on similar type projects indicate the addition of certain cation additives or foams may serve to reduce the attraction forces to water on the clay mineral surfaces. Finally it is assumed fr om the shape of the mobilized shear stress versus displacement curves that the largest magnit udes of interfacial shear strength will occur at the start of the application of shear force. Therefor the torque applied to the TBM cutter head should be at its highest value at the st art of operation, after which it is assumed the torsion force can be lowered while still main taining the same rate of excavation. Results of the modified ring shear adherence test ing indicate that stainless steel surfaces that are allowed to change from a shinny-smooth fini sh to a slightly rough feel will increase the peak adherence strength of the clay-steel interface by approximately 20%. This means that as the excavation cutter head face plates and tooling begin due to wear due to abrasion the adhesive shear strength and the potential for sticking will increase. A thorough and dynamic replacement schedule of excavation tooling or the use of more abrasion resistant metals may help to extend the time it takes for this increase in interfacial shear resistance to occur. Also, the author learned from experience that the use of any sort of semi-permeable material will have much less attraction for clay particles. This is probably because suction pressures developed at the clay-steel interface are allo wed to partially dissipate prior to shearing.

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109 8 Recommendations There have been several attempts to create simple models based on case histories to predict the occurrence of adhering clays based on fiel d observations or simple index tests. While these models provide useful indicators for identi fying potential, they full short of taking into account all of the primary geologic factors as described at the end of Section 7.3. The primary forces considered for this study incl ude the active forces generated by the thrust of the TBM and the torque applied to the spin ning cutter head as well as the passive, or mobilized, forces in the surrounding soil and pore water. The ring shear adhesion test is an appropriate test for modeling the contact pressure and torque applied to the cutter head. Some additional modifications to the apparatus could increase the utility of applying the results to the TBM industry. In order to more accurately model the action in the excavation face larger steel rings and possibly solid steel disks could be used. According to the International Tunneling Association Publication (2000) the wear on TBM cutting tools is dependent on the susceptibility of the steel to wear as well as the location of the bit on the cutter head, the average rotational speed and the pressure applied to the excavation face. Another modified testing apparatus could include the addition of cutting tools to the steel interface material. Other parameters that warrant investigation of their relative effects on adherence include the rotational velocity of the steel disk or plate and the effect of changi ng the contact pressure (confining pressure) applied during shearing. The next step in the understanding of how to overcome this prevalent issue would also includ e the testing of other kinds of materials for

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110 use in the TBM excavation and much conveyance equipment. Perhaps other types of construction grade metals, while not being as strong as low carbon steel, will have overall benefits to excavation advancement rates due to decreased sticking. Several TBM modifications have been used in previous tunnel drives including removing sharp angles, an independent rotating central cutter head and the addition of agitators which help prevent clay clumps from forming. One method that has been proven to work in preventing clay agglomeration in the TBM working chamber is the use of additives saturated with cations. Regardless, it is without question that early identification of the potential for adhering clays followed by detailed investigati on to determine the potential magnitude of the issue is paramount to the success of the project.

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111 REFERENCES Atterberg, A., 1911, Die Plastizitt der Tone. Internationale Mitteilungen fr Bodenkunde, Band 1. Ball, A., 2009, Research in soil Conditioning for EPB tunneling through difficult soils, Proceedings of the Rapid Excavation an d Tunneling Conference, Las Vegas, NV Bowden, F.P., Tabor, D., 1950, The friction and lubrication of solids, Part I. Clarenden Press,Oxford. Bowden, F.P., Tabor, D., 1964, The friction and lubrication of solids, Part II. Clarenden Press, Oxford. Braach, O., 1965, Comparison of Face Pressurized Shield Methods in Various Soil Conditions Casagrande, A., 1932, Research of Atterberg Limits of Soils, Public Records, Vol 13, No. 8, 121-136 Cerato, A. B., 2001, Influence of the Specifi c Surface Area on Geotechnical Characteristics of Fine Grained Soils, Masters Project, Dept. of Civil and Environmental Engineering, Univ. of Massachusetts, Amherst, MA Cross, T. R., 2008, Microtunneling Inc., In troduction to Microtunneling, Boulder, CO Das, B. M.., 2008, California State University, Advanced Soil Mechanics, Third Edition, Taylor and Francies Erickson E., 2005 Geotechnical Conditions and TBM Selection for the Bay Tunnel, North American Tunneling Methods Conference Proceedings Feinendegen, M., 2010, A New Laboratory Test to evaluate the probl em of clogging in mechnical tunnel driving with EPB-shields. In Rock Mechanics in Civil and Environmental Engineering, London, U.K. pp429-432 Feinendegen, M., Ziegler, M., Spagnoli, G., Fernndez-Steeger, T., Stanjek, H., 2010, A new laboratory test to evaluate the problem of cl ogging in mechanical tunnel driving with EPBshields. In: Proc. EUROCK 2010, Lausanne, Swit zerland, Taylor & Francis Group, London. Fernndez-Steeger, 2008, Interfacial processe s between mineral and tool surfaces causes, problems and solution in mechanical tunnel driving. Geotechnologien Science Report 12. 46-57. Festa, D. et al., 2012, An Investigation into the forces acting on a TBM during driving Mining the TBM logged data, Tunnelling and Underground Space Technology, Vol 32, pp 143-157

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112 Festa, D. et al., 2013, Tunnel Boring in Soft Soil: a study on the driving forces applied to a slurry-shield TBM Henkel, D. J., 1960, The Shearing Strength of Saturated Remolded Clays, Proc. Res. Conf. Shear Strength of Cohesive Soils, ASCE, pp. 533. ITA (International Tunneling association) M echanized Tunneling Working Group, 2000, Recommendations and Guidelines for Tunnel Boring Machines (TBMs), ITA-AITES, pp 1118 Kooistra, A., 1998, Delft Univesity, Apprai sal of Stickiness of Natural Clays from Laboratory Tests, Engineering Geology and Infrastructure, pp 101-113. Ingeokring Lambe, T. W. and Whitman, R. V., 1969, So il Mechanics, Wiley, New York, p. 144. Littleton, I., 1976, "An experimental study of the adhesion between clay and steel", Journal of Terramechanics, Vol. 13, No. 3, pp.141-152. Mainos et al., 2007, Evaluation of Ground In formation with Respect to EPB Tunneling for the Thessaloniki Metro, Greese, Proceeding of the 11th International Congress, Geological Society of Greese Mayne, P.W., Kemper, J.B., 1988, Profiling OCR in Stiff Clays by CPT and SPT, Geotechnical Testing Journal, ASTM, Vol 11, No. 2, 139-147. Mohr, O., 1900, Welche Umstande Bedingen di e Elastizitatsgrenze und den Bruch eines Materiales?: Zeitschrift des Vereines De utscher Ingenieuru, Vol 44, 1524-1530 Potyondy,J. G., 1961, Skin friction between various soils and construction material, Geotechnique II Vol 4, 339-353). Sagar D. I., 1999, Underpassing the Wester schelde by Implementing New Technologies, Rapid Excavation and Tunneling Conference Proceedings Skempton, A. W., 1953, The Colloidal Activi ty of Clay, Proceedings 3rd Int. Conf. Soil Mech. Found. Eng., Vol. 1, pp 57-61 Spagnoli, G., 2010, Modification of the Mechan ical behavoir of Clays for Improving TBM Tunnel Driving Spagnoli, G., 2011, Soil Conditioning for Clays in EPBMs, Tunnels and Tunneling International Spagnoli, et al., 2012, Geotechnical Aspects of Underground Construction in Soft Ground: Manipulations of Sticky Clays Regarding EPB Tunnel Driving

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113 Terzaghi, K. Peck, R., 1952, Soil Mechanics in Engineering Practice, University of Illinois, Wiley Thewes, M. and Burger, W., 2005, Clogging of TBM drives in ClayIdentification and Mitigation of Risks. Underground Space Use, Vol 2, pp 737-742 Thewes, M., 1999, Clogging Risks for TBM Drives in Clay, Tunnels & Tunneling International, pp 28-31. June Yoshimi, Y., Kishida T., 1981, "A ring torsion apparatus for evaluating friction between soil and metal Surfaces", Geotechnical Testin g Journal, Vol. 4, No. 4, pp145-152. Waays, F., 1995, The Choice Between EPB and Slu rry Shields, Selection criteria By Practical Examples, Rapid Excavation and Tunneling Conference Wykeham Farrance Engineering Limited, 1979 The Bromhead Ring Shear Manual Zimnik, A.R., van Baalen, L.R., Verhoef, P.N.W., 2000, Ngan-clay to steel surfaces. In: GeoEng 2000: AnTillgard, D.J.M.. The adherence of International Conference on Geotechnical and Zumsteg, R., & Plotze, M., 2013, Reduction of the Clogging Potential of Clays: new chemicle applications and novel quantificat ion approaches, Geotechnique, Vol No. 4, pp 276-286 Zumsteg, R. & Puzrin, A. M., 2012, Stickine ss and adhesion of conditioned clay pastes. Tunnelling Underground Space Tec hnol. 31, September, 86.

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114 Appendix A Manual For The Bromhead Ring Shear Apparatus

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127 Appendix B Specifi cations For Modified Steel Testing Rings

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3.93 2.76 0.25 #4 Flat Head Machine Screw Holes Average Surface Roughness 2mm Side View Top View 0.29 (TYP) Notes: 1) Ring Material is High Grade Steel Alloy 2) Create 3 Rings each withconsistent top surface roughness coe cient Modi ed Ring for Steel Clay Interface Tes ng By: Sean Tokarz Date: 6/20/13

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3.93 2.76 0.25 (Ave) #4 Flat Head Machine Screw Holes Rough or Ridged Surface Side View Top View 0.29 (TYP) Notes: 1) Ring Material is High Grade Steel Alloy 2) Top Surface of RingRoughness to exceed 0.2mm in roughness Modi ed Bo om Ring for Steel Clay Interface Tes ng By: Sean Tokarz Date: 10/1/13

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Multipurpose Stainless Steel (Type 304)The most widely used stainless stee l, Type 304 has go od weldability and formability and maintains corrosion resist ance up to 1500 F. Commonly used in chemical and food processing equipment. It may become slightly magnetic when worked and is not heat treatable. View information on the chemical composition of stainless steel alloys, as well as physical and mechanical properties Warning! Hardness and yield strength ar e not guaranteed and are intended only as a basis for comparison.Short RodsUnpolished (Mill) Finish Hardness: 140-223 Brinell Yield Strength: 30,000 to 35,000 psi Annealed Meet ASTM A276 and A479. Rods may be cold finished or hot rolled. Straightness tolerance is not rated. Length tolerance is 1/16" (unless noted). 3/4" Long Dia. Each 4" 9208K65 $35.63 Need help finding a product? E-mai l or call (630) 833-0300. Page 1 of McMaste r -Car r 10/14/2013 htt p ://www.mcmaster.com /

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131 Appendix C 1-D Consolidation Test, Laboratory Observations

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Laboratory Test:1 D Consolidation Test Material Type:Kaolin (white) Date:10/23/2013 Load:0.25 tsf (3.47psi) Dimensions of Sample Calculaiton Solids Initial height of sample1.005inVolume of Sample Solids1.65in Initial diameter of sample2inHeight of Sample Solids0.53in Initial Weight of Sample 0.1758lbs Initial Moisture Content 10.2% Test Parameters Specific Gravity of Solids2.65Initial Void Ratio0.912 Cross Sectional Area of Sample3.14inFinal Void Ratio0.779 Volume of Sample3.16inTotal Deformation0.070in DateTimeElapsed (sec) Elapsed (min) Deformation (in) Change (in) StrainVoid Ratio 23 Sep18:3360.100.0184 23 Sep 200.330.02100.00260.26%0.907 23 Sep 300.500.02240.00400.40%0.904 23 Sep 450.750.02400.00560.56%0.901 23 Sep 6010.02530.00690.69%0.898 23 Sep18:3512020.02920.01081.07%0.891 23 Sep18:3724040.03470.01631.62%0.881 23 Sep18:4148080.04230.02392.38%0.866 23 Sep19:273240540.05160.03323.30%0.848 23 Sep19:424140690.06480.04644.62%0.823 23 Sep20:125940990.07680.05845.81%0.800 23 Sep21:1295401590.08340.06506.47%0.788 23 Sep22:02125402090.08400.06566.53%0.787 24 Sep7:372034240339040.08660.06826.79%0.782 24 Sep18:162072580345430.08790.06956.92%0.779 Time to % Consolidation t100105mins t5055min Deformation to % Consolidation D1000.0650inches D500.05in 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (0.25tsf)

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Laboratory Test:1 D Consolidation Test Material Type:Kaolin (white) Date:10/24/2013 Load:0.5 tsf (6.94psi) Dimensions of Sample Calculaiton Solids Initial height of sample1.005inVolume of Sample Solids1.65in Initial diameter of sample2inHeight of Sample Solids0.53in Initial Weight of Sample 0.1758lbs Initial Moisture Content 10.2% Test Parameters Specific Gravity of Solids2.65Initial Void Ratio0.779 Cross Sectional Area of Sample3.14inFinal Void Ratio0.684 Volume of Sample3.16inTotal Deformation0.120in DateTimeElapsed (sec) Elapsed (min) Deformation (in) Change (in) StrainVoid Ratio 24 Sep18:3500.000.0880 24 Sep 60.100.09420.07577.53%0.768 24 Sep 120.200.09520.07677.63%0.766 24 Sep 300.500.09680.07837.79%0.763 24 Sep 6010.09860.08017.97%0.759 24 Sep18:3712020.10120.08278.23%0.754 24 Sep18:3924040.10480.08638.59%0.747 24 Sep18:4348080.10990.09149.09%0.738 24 Sep18:50900150.11600.09759.70%0.726 24 Sep19:051800300.12360.105110.46%0.712 24 Sep19:353600600.12980.111311.07%0.700 24 Sep21:34107401790.13470.116211.56%0.691 24 Sep22:01123602060.13530.116811.62%0.689 25 Sep10:402045100340850.13780.119311.87%0.685 25 Sep16:002064300344050.13810.119611.90%0.684 25 Sep18:202072700345450.13840.119911.93%0.684 Time to % Consolidation t100100mins t5020min Deformation to % Consolidation D1000.0470inches D500.0205in 0.09 0.10 0.10 0.11 0.11 0.12 0.12 0.13 0.13 0.14 0.14 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (0.5 tsf)

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Laboratory Test:1 D Consolidation Test Material Type:Kaolin (white) Date:10/25/2013 Load:1.0tsf (13.89psi) Dimensions of Sample Calculaiton Solids Initial height of sample1.005inVolume of Sample Solids1.65in Initial diameter of sample2inHeight of Sample Solids0.53in Initial Weight of Sample 0.1758lbs Initial Moisture Content 10.2% Test Parameters Specific Gravity of Solids2.65Initial Void Ratio0.912 Cross Sectional Area of Sample3.14inFinal Void Ratio0.655 Volume of Sample3.16inTotal Deformation0.135in DateTimeElapsed (sec) Elapsed (min) Deformation (in) Change (in) StrainVoid Ratio 25 Sep18:5200.000.0038 25 Sep 60.100.00430.120412.0%0.6826 25 Sep 150.250.00470.120812.0%0.6818 25 Sep 300.500.00520.121312.1%0.6808 25 Sep 6010.00580.121912.1%0.6797 25 Sep18:5412020.00690.123012.2%0.6776 25 Sep18:5624040.00840.124512.4%0.6748 25 Sep19:0048080.00980.125912.5%0.6721 25 Sep19:07900150.01270.128812.8%0.6666 25 Sep19:221800300.01400.130112.9%0.6641 25 Sep19:523600600.01660.132713.2%0.6592 25 Sep20:5272001200.01780.133913.3%0.6569 25 Sep21:3597801630.01790.134013.3%0.6567 26 Sep8:052034780339130.01840.134513.4%0.6557 26 Sep17:552070180345030.01880.134913.4%0.6550 Time to % Consolidation t10095mins t5015min Deformation to % Consolidation D1000.0140inches D500.0075in 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (1.0 tsf)

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Laboratory Test:1 D Consolidation Test Material Type:Kaolin (white) Date:10/26/2013 Load:2.0tsf (27.78psi) Dimensions of Sample Calculaiton Solids Initial height of sample1.005inVolume of Sample Solids1.65in Initial diameter of sample2inHeight of Sample Solids0.53in Initial Weight of Sample 0.1758lbs Initial Moisture Content 10.2% Test Parameters Specific Gravity of Solids2.65Initial Void Ratio0.912 Cross Sectional Area of Sample3.14inFinal Void Ratio0.645 Volume of Sample3.16inTotal Deformation0.140in DateTimeElapsed (sec) Elapsed (min) Deformation (in) Change (in) StrainVoid Ratio 26 Sep17:5600.000.0009 26 Sep 60.100.00190.135913.52%0.6531 26 Sep 150.250.00200.136013.54%0.6528 26 Sep 300.500.00220.136313.56%0.6524 26 Sep 6010.00250.136613.59%0.6518 26 Sep17:5812020.00280.136813.61%0.6513 26 Sep18:0024040.00330.137313.66%0.6504 26 Sep18:0448080.00400.138013.73%0.6491 26 Sep18:10840140.00460.138613.79%0.6479 26 Sep18:271860310.00530.139413.87%0.6465 26 Sep18:563600600.00550.139513.88%0.6462 26 Sep20:0577401290.00570.139813.91%0.6457 26 Sep20:3595401590.00580.139813.91%0.6456 26 Sep20:50104401740.00580.139813.91%0.6456 27 Sep8:132038620339770.00600.140013.93%0.6452 27 Sep12:352054340342390.00600.140113.94%0.6452 27 Sep17:232071620345270.00600.140013.93%0.6452 Time to % Consolidation t10045mins t5015min Deformation to % Consolidation D1000.0048inches D500.00256in 0.001 0.002 0.003 0.004 0.005 0.006 0.007 01101001,00010,000100,000Vertical Displacement (in)Time (mins)1 D Consolidation (2.0 tsf)

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136 Appendix D Normally Consolidat ed Ring Shear Adhesion Test, Laboratory Oobservations

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:10/25/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.5tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.0% After test60.4% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 160.00000.0000 0.00000.000.00000.006.940.000 170.024200.00000.00000.00656.500.00636.326.943.052 180.048400.00070.00070.00646.350.00616.056.942.954 190.072600.00100.00100.00606.000.00595.856.942.823 200.096800.00130.00130.00605.950.00595.906.942.823 210.1201000.00170.00170.00585.830.00606.006.942.818 220.1441200.00180.00180.00565.600.00606.006.942.763 230.1681400.00210.00210.00545.420.00606.006.942.720 240.1921600.00230.00230.00535.300.00606.006.942.692 250.2161800.00270.00270.00535.300.00605.996.942.689 260.2412000.00280.00280.00535.300.00605.986.942.687 270.2652200.00300.00300.00535.300.00605.976.942.683 280.2892400.00320.00320.00545.400.00595.946.942.700 290.3132600.00330.00330.00555.520.00595.916.942.723 300.3372800.00360.00360.00565.630.00595.916.942.748 310.3613000.00380.00380.00575.690.00595.916.942.762 320.3853200.00400.00400.00575.700.00605.956.942.775 330.4093400.00400.00400.00585.800.00606.036.942.817 340.4333600.00430.00430.00585.800.00616.056.942.823 350.4573800.00480.00480.00585.800.00616.106.942.835

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:10/28/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:1tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.0% After test51.5% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0013.890.000 10.024200.00000.00000.011011.000.012312.2713.895.542 20.048400.00090.00090.011011.000.012312.2713.895.542 30.072600.00120.00120.011010.990.011811.8313.895.437 40.096800.00190.00190.010910.860.011611.6013.895.350 50.1201000.00200.00200.010810.800.011411.4013.895.288 60.1441200.00220.00220.010810.800.011211.2013.895.240 70.1681400.00280.00280.010710.730.011211.2013.895.224 80.1921600.00300.00300.010710.670.011111.1313.895.193 90.2161800.00320.00320.010610.640.011111.0713.895.170 100.2412000.00350.00350.010610.600.011211.1713.895.185 110.2652200.00400.00400.010610.600.011211.1713.895.185 120.2892400.00430.00430.010610.570.011111.1213.895.165 130.3132600.00450.00450.010510.530.011111.0713.895.145 140.3372800.00460.00460.010510.510.011111.0713.895.140 150.3613000.00500.00500.010510.470.011111.0713.895.131 160.3853200.00510.00510.010510.470.011111.0913.895.134 170.4093400.00550.00550.010510.470.011111.1213.895.142 180.4333600.00570.00570.010510.470.011211.2113.895.164 190.4573800.00590.00590.010510.500.011311.2713.895.185 200.4814000.00600.00600.010510.480.011211.2513.895.175

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:10/30/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:2tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test74.0% After test44.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0027.780.000 0.50.0120.00000.00000.017017.000.00686.8027.785.669 10.024200.00100.00100.018918.900.020320.3027.789.337 20.048400.00200.00200.013313.300.024124.1027.788.909 30.072600.00250.00250.012612.550.023123.1027.788.492 40.096800.00300.00300.011911.920.022422.4027.788.175 50.1201000.00320.00320.011811.750.022222.1527.788.075 60.1441200.00380.00380.011411.400.022022.0027.787.956 70.1681400.00400.00400.011311.300.022021.9527.787.920 80.1921600.00420.00420.011311.250.021921.8827.787.891 90.2161800.00490.00490.011211.240.021821.7527.787.858 100.2412000.00500.00500.011311.250.021621.6127.787.827 110.2652200.00540.00540.011211.200.021621.6227.787.818 120.2892400.00580.00580.011211.200.021621.6427.787.822 130.3132600.00600.00600.011211.180.021721.7027.787.832 140.3372800.00610.00610.011111.120.021721.7027.787.818 150.3613000.00640.00640.011111.100.021721.7027.787.813 160.3853200.00680.00680.011111.130.021721.6527.787.808 170.4093400.00700.00700.011011.000.021721.6527.787.777 180.4333600.00720.00720.00929.200.021721.7027.787.360 190.4573800.00740.00740.00939.300.021721.6827.787.379 Page 1 of 2

PAGE 152

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:10/30/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:2tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test74.0% After test44.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00780.00780.00929.200.021721.7027.787.360 Page 2 of 2

PAGE 153

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/1/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:1tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.8% After test67.8% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0013.890.000 0.50.0120.000200.020020.000.00090.903.474.978 10.024200.00020.00020.019019.000.00090.9013.894.740 20.048400.00020.00020.017017.000.00101.0013.894.288 30.072600.00180.00180.017017.000.00121.2013.894.335 40.096800.00170.00170.017017.000.00151.5013.894.407 50.1201000.00200.00200.017017.000.00171.7013.894.454 60.1441200.00200.00200.017017.000.00171.7013.894.454 70.1681400.00250.00250.016016.000.00161.6013.894.192 80.1921600.00290.00290.015915.900.00161.5513.894.157 90.2161800.00300.00300.015915.900.00151.5013.894.145 100.2412000.00320.00320.015015.000.00151.5013.893.930 110.2652200.00370.00370.014714.700.00151.4713.893.852 120.2892400.00390.00390.013813.800.00141.3813.893.616 130.3132600.00410.00410.013813.800.00141.3813.893.616

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/6/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.0% After test40.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0027.780.000 10.024200.00100.00100.016016.000.022022.0027.789.051 20.048400.00120.00120.015215.200.025625.6027.789.718 30.072600.00190.00190.014514.500.025025.0027.789.409 40.096800.00200.00200.013913.900.024324.3027.789.099 50.1201000.00270.00270.013613.550.023823.8027.788.897 60.1441200.00300.00300.013113.100.023623.6027.788.742 70.1681400.00330.00330.012812.800.023623.6027.788.670 80.1921600.00380.00380.012612.600.023523.4527.788.587 90.2161800.00400.00400.012512.500.023323.3427.788.537 100.2412000.00440.00440.012312.300.023423.4027.788.504 110.2652200.00450.00450.012312.250.023423.4027.788.492 120.2892400.00500.00500.012112.130.023423.4027.788.463 130.3132600.00510.00510.012212.170.023423.4027.788.473 140.3372800.00550.00550.012112.050.023523.4527.788.456 150.3613000.00580.00580.012012.030.023523.5027.788.463 160.3853200.00600.00600.012012.030.023523.4527.788.451 170.4093400.00600.00600.012012.000.023623.5527.788.468 180.4333600.00600.00600.011911.900.023423.3527.788.396 190.4573800.00600.00600.011911.870.023423.3527.788.389 Page 1 of 2

PAGE 155

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/6/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.0% After test40.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00580.00580.011911.860.023423.3527.788.387 210.5054200.00580.00580.011911.850.023423.3527.788.384 220.5294400.00580.00580.011811.800.023423.3527.788.373 230.5534600.00570.00570.011811.800.023323.3027.788.361 240.5774800.00570.00570.011811.780.023323.3027.788.356 250.6015000.00570.00570.011811.780.023323.3027.788.356 Page 2 of 2

PAGE 156

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/6/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test73.1% After test75.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.003.470.000 10.024200.00000.00000.00151.500.00191.903.470.810 20.048400.00050.00050.00131.300.00161.603.470.691 30.072600.00120.00120.00121.200.00181.803.470.715 40.096800.00200.00200.00707.000.00111.103.471.929 50.1201000.00290.00290.00606.000.00121.203.471.715 60.1441200.00380.00380.00303.000.00101.003.470.953 70.1681400.00450.00450.00050.500.00090.903.470.333 80.1921600.00500.00500.00020.200.00090.903.470.262 90.2161800.00550.00550.00303.000.00111.103.470.977 100.2412000.00600.00600.00323.200.00131.253.471.060 110.2652200.00630.00630.00212.100.00151.503.470.858 120.2892400.00680.00680.00202.000.00171.703.470.881 130.3132600.00730.00730.00212.100.00212.103.471.000 140.3372800.00790.00790.00212.100.00242.353.471.060 150.3613000.00830.00830.00212.100.00212.103.471.000 160.3853200.00870.00870.00212.100.00212.103.471.000 170.4093400.00910.00910.00212.100.00232.303.471.048 180.4333600.00980.00980.00212.100.00242.403.471.072 190.4573800.01000.01000.00212.100.00242.403.471.072 Page 1 of 2

PAGE 157

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/6/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test73.1% After test75.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.01030.01030.00212.100.00232.303.471.048 210.5054200.01100.01100.00212.100.00242.403.471.072 220.5294400.01120.01120.00212.100.00242.403.471.072 Page 2 of 2

PAGE 158

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/8/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:1ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.0% After test54.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0013.890.000 0.50.0120.00000.021021.000.011011.0013.897.622 10.024200.00100.00100.021021.000.011011.0013.897.622 20.048400.00200.00200.019119.100.010510.5013.897.051 30.072600.00380.00380.018118.100.010510.5013.896.812 40.096800.00410.00410.017917.900.010310.3013.896.717 50.1201000.00500.00500.017417.400.00999.9013.896.503 60.1441200.00570.00570.017017.000.00979.6513.896.348 70.1681400.00620.00620.016816.800.00969.6013.896.288 80.1921600.00660.00660.016616.550.00979.7013.896.253 90.2161800.00710.00710.016616.550.00989.7513.896.265 100.2412000.00750.00750.016616.550.00979.7013.896.253 110.2652200.00800.00800.016616.550.00979.7013.896.253 120.2892400.00850.00850.016616.550.00989.7513.896.265 130.3132600.00890.00890.016616.550.00989.7813.896.272 140.3372800.00930.00930.016616.550.00989.8013.896.276 150.3613000.00960.00960.016516.500.00999.9013.896.288 160.3853200.00990.00990.016516.450.010410.3513.896.384 170.4093400.01040.01040.016516.500.010210.2013.896.360 180.4333600.01050.01050.016516.450.010210.2013.896.348 Page 1 of 2

PAGE 159

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/8/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:1ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.0% After test54.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 190.4573800.01100.01100.016616.600.010310.2513.896.396 200.4814000.01130.01130.016616.600.010410.3513.896.419 210.5054200.01150.01150.016316.300.010310.2513.896.324 220.5294400.01180.01180.016216.150.010410.3513.896.312 230.5534600.01200.01200.015915.900.010310.2513.896.229 240.5774800.01240.01240.016015.980.010510.5013.896.307 250.6015000.01250.01250.015915.900.010510.5013.896.288 Page 2 of 2

PAGE 160

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/15/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.8% After test67.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.006.940.000 0.50.0120.00000.00797.900.00939.306.944.097 10.024200.00040.00040.00646.400.00919.106.943.692 20.048400.00070.00070.00494.900.00838.306.943.144 30.072600.00090.00090.00414.100.00828.176.942.923 40.096800.00110.00110.00333.300.00818.056.942.704 50.1201000.00140.00140.00272.700.00757.506.942.430 60.1441200.00150.00150.00252.500.00727.206.942.311 70.1681400.00170.00170.00252.450.00787.806.942.442 80.1921600.00180.00180.00242.360.00727.206.942.277 90.2161800.00190.00190.00232.300.00757.506.942.334 100.2412000.00200.00200.00222.220.00777.706.942.363 110.2652200.00210.00210.00222.220.00767.606.942.339 120.2892400.00220.00220.00232.300.00777.656.942.370 130.3132600.00220.00220.00222.220.00777.706.942.363 140.3372800.00230.00230.00212.060.00777.686.942.320 150.3613000.00240.00240.00201.980.00787.816.942.332 160.3853200.00240.00240.00191.850.00797.906.942.322 170.4093400.00250.00250.00181.800.00818.106.942.358 180.4333600.00260.00260.00181.780.00828.156.942.365 Page 1 of 2

PAGE 161

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/15/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.8% After test67.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 190.4573800.00260.00260.00171.680.00828.206.942.353 200.4814000.00270.00270.00161.620.00838.276.942.356 210.5054200.00280.00280.00151.460.00828.206.942.301 220.5294400.00280.00280.00141.430.00848.406.942.341 230.5534600.00290.00290.00131.300.00848.406.942.311 240.5774800.00290.00290.00131.280.00858.456.942.318 250.6015000.00300.00300.00121.210.00878.706.942.361 Page 2 of 2

PAGE 162

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/16/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test73.1% After test54.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.003.470.000 10.024200.00500.00500.00222.150.00232.273.471.052 20.048400.00500.00500.00212.100.00222.223.471.028 30.072600.00500.00500.00212.050.00222.163.471.003 40.096800.00500.00500.00202.000.00212.113.470.979 50.1201000.00500.00500.00201.980.00212.083.470.967 60.1441200.00500.00500.00201.980.00212.083.470.967 70.1681400.00500.00500.00201.980.00212.083.470.967 80.1921600.00500.00500.00201.950.00212.063.470.955 90.2161800.00500.00500.00201.950.00212.063.470.955 100.2412000.00500.00500.00201.950.00212.063.470.955 110.2652200.00500.00500.00201.950.00212.063.470.955 120.2892400.00500.00500.00201.950.00212.063.470.955 130.3132600.00550.00550.00191.900.00202.003.470.930 140.3372800.00600.00600.00181.810.00191.913.470.887 150.3613000.00600.00600.00181.780.00191.873.470.869 160.3853200.00600.00600.00171.730.00181.823.470.844 170.4093400.00600.00600.00171.700.00181.793.470.832 180.4333600.00600.00600.00171.680.00181.773.470.820 190.4573800.00600.00600.00171.690.00181.783.470.826 Page 1 of 2

PAGE 163

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/16/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test73.1% After test54.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00600.00600.00171.650.00171.743.470.808 210.5054200.00600.00600.00161.630.00171.713.470.795 220.5294400.00600.00600.00161.630.00171.713.470.795 230.5534600.00600.00600.00161.600.00171.693.470.783 240.5774800.00600.00600.00171.650.00171.743.470.808 Page 2 of 2

PAGE 164

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/19/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.5% After test55.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.006.940.000 10.024200.00000.00000.00505.000.010610.556.943.704 20.048400.00020.00020.00454.500.00959.506.943.334 30.072600.00050.00050.00434.300.00919.076.943.185 40.096800.00070.00070.00434.300.00919.076.943.185 50.1201000.00090.00090.00444.400.00939.286.943.259 60.1441200.00110.00110.00464.600.00979.716.943.408 70.1681400.00120.00120.00464.600.00979.716.943.408 80.1921600.00150.00150.00464.600.00979.716.943.408 90.2161800.00180.00180.00464.600.00979.716.943.408 100.2412000.00210.00210.00464.600.00979.716.943.408 110.2652200.00210.00210.00464.620.00979.756.943.422 120.2892400.00220.00220.00464.580.00979.666.943.393 130.3132600.00240.00240.00484.840.010210.216.943.585 140.3372800.00270.00270.00464.600.00979.716.943.408 150.3613000.00280.00280.00454.520.00959.546.943.348 160.3853200.00300.00300.00464.640.00989.796.943.437 170.4093400.00320.00320.00494.940.010410.426.943.660 180.4333600.00330.00330.00484.800.010110.136.943.556 190.4573800.00350.00350.00484.800.010110.136.943.556 Page 1 of 2

PAGE 165

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/19/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.5% After test55.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00370.00370.00484.840.010210.216.943.585 210.5054200.00390.00390.00484.840.010210.216.943.585 220.5294400.00400.00400.00464.640.00989.796.943.437 230.5534600.00410.00410.00484.800.010110.136.943.556 240.5774800.00430.00430.00484.760.010010.046.943.526 250.6015000.00460.00460.00474.680.00999.876.943.467 Page 2 of 2

PAGE 166

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/20/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:1ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.1% After test#DIV/0!% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0013.890.000 10.024200.00200.00200.012312.300.013012.9813.896.021 20.048400.00200.00200.012312.300.013012.9813.896.021 30.072600.00300.00300.012112.100.012812.7713.895.923 40.096800.00370.00370.011811.800.012412.4513.895.776 50.1201000.00410.00410.011511.500.012112.1313.895.629 60.1441200.00480.00480.011311.300.011911.9213.895.531 70.1681400.00520.00520.011311.250.011911.8713.895.507 80.1921600.00570.00570.011211.200.011811.8213.895.482 90.2161800.00620.00620.011311.300.011911.9213.895.531 100.2412000.00680.00680.011411.350.012011.9713.895.556 110.2652200.00720.00720.011111.050.011711.6613.895.409 120.2892400.00770.00770.011111.050.011711.6613.895.409 130.3132600.00810.00810.011010.950.011611.5513.895.360 140.3372800.00850.00850.010510.500.011111.0813.895.140 150.3613000.00910.00910.010710.700.011311.2913.895.238 160.3853200.00950.00950.011911.900.012612.5513.895.825 170.4093400.00970.00970.011711.700.012312.3413.895.727 180.4333600.01030.01030.011711.700.012312.3413.895.727 190.4573800.01030.01030.011711.700.012312.3413.895.727

PAGE 167

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/22/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.4% After test#DIV/0!% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0027.780.000 10.024200.00050.00050.017117.060.020720.6927.788.992 20.048400.00090.00090.017817.810.021621.6027.789.387 30.072600.00120.00120.017317.310.021020.9927.789.124 40.096800.00150.00150.017117.060.020720.6927.788.992 50.1201000.00200.00200.016916.860.020420.4527.788.887 60.1441200.00220.00220.016716.690.020220.2327.788.794 70.1681400.00230.00230.016616.630.020220.1627.788.762 80.1921600.00260.00260.016516.530.020020.0427.788.712 90.2161800.00290.00290.016516.470.020019.9727.788.679 100.2412000.00310.00310.016316.310.019819.7827.788.597 110.2652200.00330.00330.016316.250.019719.7027.788.564 120.2892400.00370.00370.016216.180.019619.6127.788.524 130.3132600.00380.00380.016116.060.019519.4827.788.465 140.3372800.00410.00410.015915.940.019319.3227.788.399 150.3613000.00430.00430.015915.890.019319.2727.788.376 160.3853200.00450.00450.015815.840.019219.2127.788.350 170.4093400.00480.00480.015815.810.019219.1727.788.333 180.4333600.00490.00490.015815.750.019119.1027.788.300 190.4573800.00500.00500.015715.690.019019.0227.788.267 Page 1 of 2

PAGE 168

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:11/22/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.4% After test#DIV/0!% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00520.00520.015815.810.019219.1727.788.333 210.5054200.00530.00530.015615.630.018918.9527.788.235 220.5294400.00550.00550.015515.530.018818.8327.788.185 230.5534600.00600.00600.015515.500.018818.7927.788.169 240.5774800.00610.00610.015515.470.018818.7627.788.152 250.6015000.00620.00620.015415.380.018618.6427.788.103 Page 2 of 2

PAGE 169

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/2/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.0% After test44.1% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0027.780.000 10.024200.00100.00100.014414.400.017617.6027.787.622 20.048400.00120.00120.013713.680.020520.4827.788.137 30.072600.00190.00190.013113.050.020020.0027.787.872 40.096800.00200.00200.012512.510.019419.4427.787.610 50.1201000.00270.00270.012212.200.019019.0427.787.440 60.1441200.00300.00300.011811.790.018918.8827.787.305 70.1681400.00330.00330.011511.520.018918.8827.787.241 80.1921600.00380.00380.011311.340.018818.7627.787.170 90.2161800.00400.00400.011311.250.018718.6727.787.127 100.2412000.00440.00440.011111.070.018718.7227.787.096 110.2652200.00450.00450.011011.030.018718.7227.787.085 120.2892400.00500.00500.010910.920.018718.7227.787.059 130.3132600.00510.00510.011010.950.018718.7227.787.068 140.3372800.00550.00550.010810.850.018818.7627.787.052 150.3613000.00580.00580.010810.830.018818.8027.787.057 160.3853200.00600.00600.010810.830.018818.7627.787.048 170.4093400.00600.00600.010810.800.018818.8427.787.060 180.4333600.00600.00600.010710.710.018718.6827.787.001 190.4573800.00600.00600.010710.680.018718.6827.786.994 Page 1 of 2

PAGE 170

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/2/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:2ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.0% After test44.1% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00580.00580.010710.670.018718.6827.786.992 210.5054200.00580.00580.010710.670.018718.6827.786.990 220.5294400.00580.00580.010610.620.018718.6827.786.979 230.5534600.00570.00570.010610.620.018618.6427.786.970 Page 2 of 2

PAGE 171

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/13/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.8% After test 114.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.003.470.000 10.024200.00150.00150.00020.200.00646.403.471.572 20.048400.00250.00250.00020.200.00626.203.471.524 30.072600.00300.00300.00020.200.00626.203.471.524 40.096800.00350.00350.00020.200.00565.603.471.382 50.1201000.00400.00400.00020.200.00626.203.471.524 60.1441200.00460.00460.00010.100.00434.303.471.048 70.1681400.00510.00510.00010.100.00373.703.470.905 80.1921600.00530.00530.00010.100.00313.103.470.762 90.2161800.00570.00570.00020.150.00363.603.470.893 100.2412000.00610.00610.00010.100.00363.603.470.881 110.2652200.00630.00630.00010.100.00343.403.470.834 120.2892400.00680.00680.00010.100.00323.203.470.786 130.3132600.00700.00700.00030.250.00323.203.470.822 140.3372800.00740.00740.00030.250.00323.203.470.822 150.3613000.00780.00780.00030.250.00323.203.470.822 160.3853200.00800.00800.00040.350.00323.203.470.846 170.4093400.00820.00820.00040.350.00323.203.470.846 180.4333600.00850.00850.00030.250.00323.203.470.822 190.4573800.00880.00880.00030.250.00323.203.470.822 Page 1 of 2

PAGE 172

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/13/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test72.8% After test 114.7% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00910.00910.00020.200.00323.203.470.810 210.5054200.00940.00940.00020.200.00323.203.470.810 220.5294400.01010.01010.00020.150.00323.203.470.798 230.5534600.01040.01040.00101.000.00323.203.471.000 240.5774800.01090.01090.00101.000.00323.203.471.000 250.6015000.01120.01120.00101.000.00323.203.471.000 Page 2 of 2

PAGE 173

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/13/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.25tsf thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.8% After test60.2% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.003.470.000 0.50.0120.00000.00262.600.00212.103.471.120 10.024200.00000.00000.00222.200.00181.803.470.953 20.048400.00250.00250.00212.050.00201.953.470.953 30.072600.00310.00310.00181.800.00181.803.470.858 40.096800.00400.00400.00201.950.00202.003.470.941 50.1201000.00520.00520.00252.500.00252.503.471.191 60.1441200.00590.00590.00212.100.00222.203.471.024 70.1681400.00680.00680.00181.800.00222.203.470.953 80.1921600.00720.00720.00151.500.00202.003.470.834 90.2161800.00810.00810.00101.000.00202.003.470.715 100.2412000.00880.00880.00090.920.00222.203.470.743 110.2652200.00940.00940.00070.700.00202.003.470.643 120.2892400.01000.01000.00070.650.00212.103.470.655 130.3132600.01080.01080.00050.520.00212.103.470.624 140.3372800.01110.01110.00050.480.00212.103.470.615 150.3613000.01190.01190.00010.100.00212.103.470.524 160.3853200.01120.01120.00010.100.00212.103.470.524 170.4093400.01300.01300.00000.000.00212.103.470.500 180.4333600.01330.01330.00000.000.00202.003.470.476 190.4573800.01400.01400.00000.000.00191.903.470.453 200.4814000.01420.01420.00000.000.00202.003.470.476

PAGE 174

Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/13/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test74.9% After test58.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.006.940.000 10.024200.00050.00050.00595.850.00858.506.943.418 20.048400.00100.00100.00595.850.00848.406.943.394 30.072600.00130.00130.00595.900.00828.206.943.359 40.096800.00170.00170.00595.900.00818.106.943.335 50.1201000.00210.00210.00595.900.00808.026.943.316 60.1441200.00250.00250.00595.900.00808.006.943.311 70.1681400.00280.00280.00595.900.00808.006.943.311 80.1921600.00300.00300.00595.850.00807.956.943.287 90.2161800.00340.00340.00585.800.00797.906.943.263 100.2412000.00380.00380.00595.870.00797.856.943.268 110.2652200.00410.00410.00585.750.00797.856.943.239 120.2892400.00430.00430.00575.700.00787.806.943.216 130.3132600.00460.00460.00575.650.00787.756.943.192 140.3372800.00490.00490.00575.650.00767.606.943.156 150.3613000.00510.00510.00575.650.00767.606.943.156 160.3853200.00530.00530.00565.620.00777.656.943.161 170.4093400.00550.00550.00575.680.00767.636.943.170 180.4333600.00580.00580.00565.600.00767.626.943.149 190.4573800.00610.00610.00565.600.00767.626.943.149 Page 1 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:12/13/2013 Test Type:Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent2m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test74.9% After test58.3% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00650.00650.00565.600.00767.626.943.149 210.5054200.00650.00650.00565.600.00777.656.943.156 220.5294400.00670.00670.00565.600.00777.676.943.161 230.5534600.00690.00690.00565.600.00777.676.943.161 Page 2 of 2

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164 Appendix E Overly Consolidated Ring Shear Adhesion Test, Laboratory Observations

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/7/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:8.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test71.9% After test48.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.003.470.000 10.024200.00000.00000.021321.300.029029.003.4711.981 20.048400.00000.00000.020820.800.027827.803.4711.576 30.072600.00000.00000.020120.100.026426.403.4711.076 40.096800.00000.00000.019119.100.025525.503.4710.624 50.1201000.00000.00000.018718.700.024624.603.4710.314 60.1441200.00000.00000.018318.300.023423.403.479.933 70.1681400.00020.00020.018118.100.022222.203.479.599 80.1921600.00030.00030.017817.800.021921.903.479.456 90.2161800.00050.00050.017617.600.021521.503.479.313 100.2412000.00060.00060.017517.500.021221.203.479.218 110.2652200.00060.00060.017317.300.021121.103.479.147 120.2892400.00070.00070.017117.100.020920.903.479.051 130.3132600.00090.00090.017017.000.020820.803.479.004 140.3372800.00090.00090.017017.000.020720.703.478.980 150.3613000.00100.00100.017017.000.020720.653.478.968 160.3853200.00100.00100.016916.900.020620.603.478.932 170.4093400.00100.00100.016816.800.020620.603.478.909 180.4333600.00100.00100.016716.700.020620.603.478.885 190.4573800.00100.00100.016716.700.020520.503.478.861 Page 1 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/7/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.25ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:8.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test71.9% After test48.6% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00100.00100.016616.600.020520.503.478.837 210.5054200.00100.00100.016616.550.020520.503.478.825 220.5294400.00110.00110.016516.500.020520.453.478.801 230.5534600.00110.00110.016516.500.020520.453.478.801 240.5774800.00110.00110.016316.300.020420.403.478.742 250.6015000.00120.00120.016216.200.020420.403.478.718 260.6255200.00120.00120.016216.200.020420.353.478.706 270.6495400.00120.00120.016216.150.020320.303.478.682 280.6735600.00130.00130.016116.100.020320.303.478.670 Page 2 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/13/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:1ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:2.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.9% After test41.0% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.0013.890.000 10.024200.00000.00000.025025.000.018518.5013.8910.362 20.04840 0.0050 0.00500.024124.100.017817.8013.899.980 30.07260 0.0070 0.00700.023223.200.017117.1013.899.599 40.09680 0.0060 0.00600.022822.800.016816.8013.899.433 50.120100 0.0040 0.00400.022122.100.016016.0013.899.075 60.144120 0.0020 0.00200.021821.800.015615.6013.898.909 70.168140 0.0020 0.00200.021821.800.015515.5013.898.885 80.192160 0.0010 0.00100.021421.400.015215.2013.898.718 90.2161800.00000.00000.021321.300.015115.1013.898.670 100.2412000.00000.00000.021221.200.015115.1013.898.647 110.2652200.00000.00000.020820.800.014814.8013.898.480 120.2892400.00100.00100.020820.800.014614.6013.898.432 130.3132600.00100.00100.020720.700.014514.5013.898.384 140.3372800.00200.00200.020620.600.014514.5013.898.361 150.3613000.00200.00200.020620.600.014414.4013.898.337 160.3853200.00200.00200.020620.600.014314.3013.898.313 170.4093400.00300.00300.020520.500.014314.3013.898.289 180.4333600.00300.00300.020420.400.014214.2013.898.242 190.4573800.00400.00400.020420.400.014214.2013.898.242 Page 1 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/13/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:1ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:2.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test70.9% After test41.0% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00500.00500.020420.400.014214.2013.898.242 210.5054200.00600.00600.020420.400.014114.1013.898.218 220.5294400.00700.00700.020320.300.014114.1013.898.194 230.5534600.00800.00800.020320.300.014114.1013.898.194 240.5774800.00900.00900.020220.200.014014.0013.898.146 250.6015000.01000.01000.020220.200.014014.0013.898.146 260.6255200.01000.01000.020220.200.014014.0013.898.146 270.6495400.01000.01000.020220.200.014014.0013.898.146 Page 2 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/20/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:4.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test71.2% After test45.5% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 00.00000.0000 0.00000.000.00000.006.940.000 10.024200.00000.00000.022222.200.024724.706.9411.171 20.04840 0.0010 0.00100.021521.500.023923.906.9410.814 30.07260 0.0020 0.00200.020520.500.022922.906.9410.338 40.09680 0.0030 0.00300.019419.400.022022.006.949.861 50.120100 0.0030 0.00300.019119.100.021521.506.949.671 60.144120 0.0020 0.00200.018518.500.021121.106.949.433 70.168140 0.0010 0.00100.018118.100.020820.806.949.266 80.192160 0.0010 0.00100.017817.800.020620.606.949.147 90.216180 0.0010 0.00100.017417.400.020320.306.948.980 100.241200 0.0010 0.00100.017117.050.020120.056.948.837 110.265220 0.0010 0.00100.016916.850.019919.906.948.754 120.2892400.00000.00000.016516.500.019619.606.948.599 130.3132600.00000.00000.016316.300.019619.606.948.551 140.3372800.00000.00000.016316.300.019619.606.948.551 150.3613000.00000.00000.016116.100.019619.606.948.504 160.3853200.00100.00100.015915.900.019419.406.948.408 170.4093400.00100.00100.015715.700.019119.106.948.289 180.4333600.00100.00100.015515.500.019019.006.948.218 190.4573800.00100.00100.015515.500.019019.006.948.218 Page 1 of 2

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Laboratory Test:Ring Shear Adhesion Test Material Type:Kaolin (white) Date:2/20/2014 Test Type:Over Consolidated Undrained Ring Volume Test Parameters Inside diameter2.756inchesRing Roughness Coefficent20m Outside diameter3.937inchesConfining Pressure:0.5ts f thickness1.181inchesGear Ratio:30 60 height0.197inchesSpeed:3.0Deg/Min Area6.21 in OCR:4.0 Volume1.22 in3Moisture Content Tourqu are length2.5inPrior to test71.2% After test45.5% Degrees Shear Displacement (in) Time (sec) Vertical Gage Reading (in) Consolidation (in) South Force Gage Reading (in) South Force Gage Reading (lbs) North Force Gage Reading (in) North Force Gage Reading (lbs) Normal Stress (psi) Shear Stress (psi) 200.4814000.00150.00150.015315.300.018918.906.948.146 210.5054200.00200.00200.015215.200.018918.906.948.122 220.5294400.00200.00200.015115.050.018818.806.948.063 230.5534600.00250.00250.015015.000.018818.806.948.051 240.5774800.00250.00250.014914.900.018818.806.948.027 250.6015000.00300.00300.014914.900.018818.806.948.027 260.6255200.00300.00300.014814.800.018718.706.947.980 270.6495400.00300.00300.014814.800.018518.506.947.932 Page 2 of 2