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Measuring load-deformation properties of geotextiles using the simplified intrinsic confined test

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Measuring load-deformation properties of geotextiles using the simplified intrinsic confined test
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Ballegeer, John Patrick
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English
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viii, 78 leaves : illustrations ; 29 cm

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Subjects / Keywords:
Geotextiles ( lcsh )
Soil stabilization ( lcsh )
Geotextiles ( fast )
Soil stabilization ( fast )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Bibliography:
Includes bibliographical references (leaves 76-78).
General Note:
Submitted in partial fulfillment of the requirements for the degree, Master of Science, Civil Engineering.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by John Patrick Ballegeer.

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|University of Colorado Denver
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Auraria Library
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ocm30839224
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Full Text
MEASURING LOAD-DEFORMATION PROPERTIES OF GEOTEXTILES
USING THE SIMPLIFIED INTRINSIC CONFINED TEST
by
John Patrick Ballegeer
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado at Denver
in partial fulfillment
of the requirements for the degree of
Master of Science
Civil Engineering
1993


This thesis for the Master of Science
degree by
John Patrick Ballegeer
has been approved for the
Department of
Civil Engineering

Date


Ballegeer, John Patrick (M.S., Civil Engineering)
Measuring Load-deformation Properties of Geotextiles
Using the Simplified Intrinsic Confined Test
Thesis directed by Associate Professor Jonathan T. H. Wu
ABSTRACT
Soils lacking the engineering properties necessary
for construction of earthen structures can be improved by
soil-reinforcement techniques. Application of soil-
reinforcement techniques can improve slope stabilities,
improve drainage characteristics in soils, increase
retaining wall stability and settlement tolerance, reduce
costs, increase corrosion resistance, and transfer
vertical stresses away from weak zones in nonuniform
foundations.
Designing geotextile-reinforced earthen structures
requires knowledge of the load-deformation properties of
the geotextile. Ideally, these properties are determined
by laboratory tests that simulate operational conditions.
Most laboratory test methods simulate operational
conditions by confining the geotextile in soil that is
held stationary while the geotextile deforms. Relative
movement between the soil and the geotextile induces
resistive forces in the confining soil. The load-
iii


deformation properties measured by the test include both
the tensile strength of the geotextile and the added
resistive forces in the confining soil. These load-
deformation properties, if used in design, can result in
erroneously high factors of safety or possibly unsafe
designs.
A new test method, the Intrinsic Confined Test, was
developed to test a geotextile under operational
conditions typical of geotextile-reinforced earthen
structures. This test method used a rubber membrane, a
thin soil layer and a vacuum to apply a uniform confining
pressure over the entire geotextile specimen. The method
allowed compatible strain between the confining soil and
geotextile. Compatible strains eliminated the induced
resistive forces in the confining soils and the test
measured the true load-deformation properties of the
geotextile.
This thesis presents a simplified version of the
Intrinsic Confined Test. The simplified method involves
a simplified apparatus and procedure that performs the
Intrinsic Confined Test using only a thin rubber membrane
as the confining material. The result is a more uniform
and standardized test method that is performed easily and
quickly.
Five different geotextiles were tested using the
IV


simplified Intrinsic Confined Test method. Test results
demonstrated that the method provides a simple and
reliable alternative capable of measuring the intrinsic
confined properties of geotextiles under typical
operational conditions. Test results also demonstrated
the effects of confining pressures on different
geotextile types.
This abstract accurately represents the content of the
candidate's thesis. I recommend its publication.
Signed
v


ACKNOWLEDGEMENTS
The University of Colorado, Denver, for providing testing
facilities and funding. Dr. Jonathan T. H. Wu, Associate
Professor at the University of Colorado, Denver, for
providing his time, assistance and counsel throughout the
research, testing and preparation of this thesis.
Mirafi, Inc., Hoechst Celanese Corp., and Gundel Lining
Systems, Inc. for providing product information and
geotextile materials.
vi


CONTENTS
Chapter
1. Introduction........................................ 1
1.1 Problem Statement...................................5
1.2 Research Objectives ............................... 6
1.3 Methods of Research ............................... 6
1.4 Outline of Thesis...................................8
2. Background.......................................... 10
2.1 Physical Characteristics .......................... 10
2.2 Load-Deformation Properties ....................... 16
2.3 Geotextile Testing Methods ........................ 22
2.3.1 Confined Test Methods........................... 23
3. Intrinsic Confined Test............................. 32
3.1 Test Apparatus.................................... 34
3.2 Test Materials..................................... 37
3.3 Specimen Preparation .............................. 39
3.4 Test Procedure................................. 43
4. Test Results and Discussion of Test Results ... 48
4.1 Non-woven Needle-punched Geotextiles .............. 50
4.2 Non-woven Heat-bonded Geotextiles ................. 51
4.3 Woven Geotextile .................................. 55
4.4 Design Implications ............................... 58
5. Summary and Conclusions............................. 60
5.1 Summary........................................... 60-
vii


5.2 Conclusions....................................... 61
5.3 Recommendations for Further Study ................ 62
Appendix
A. Selected Test Data................................ 64
References............................................ 76
viii


1. Introduction
The design and construction of any earthen structure
is largely dependant upon the locally available
construction materials. When available local soils lack
the engineering properties required for the proposed
design they are often excavated and replaced by suitable
soils imported -to the site at significant cost. A viable
alternative to replacing unsuitable soils is to improve
the engineering properties of the local soils by applying
soil reinforcement techniques. Soil reinforcement
combines soil and non-soil materials to form a composite
material having superior properties. Soils, having high
compressive strengths and low tensile strengths are
combined with natural or synthetic materials having high
tensile strengths. The resulting interaction between the
two dissimilar materials improves the engineering
properties of the overall soil mass.
Soil reinforcement techniques are not new. For
thousands of years a variety of non-soil materials have
been used to improve the engineering properties of soils.
Corduroy roads were constructed in the United Kingdom as
early as-2500 B.C. Ancient Babylonian Temples
1


(ziggurats) found in Iraq used soil reinforcement over
3,000 years ago. The Ancient Romans constructed reed-
reinforced earth levies along the Tiber River. Even in
Colonial North America, levee and road embankments were
reinforced by constructing them directly on the brush and
small trees that commonly grew on the marshy ground
(Holtz and Christopher 1984; Bonaparte, Holtz, and Giroud
1987).
Our modern soil reinforcement techniques make use of
stronger and more uniform man-made textile materials.
The first recorded application of a textile as a soil
reinforcement material in the United States was a road
construction project completed in South Carolina during
the 1930's. This early application used a woven cotton
fabric as the reinforcing material. During the 1960's,
manufactured synthetic fabrics called geotextiles became
widely used for erosion control in the U.S. and in
Europe. More recently, geotextiles were first used in
1971 to construct earthen embankments over soft
foundation soils (Holtz and Christopher 1984).
Geotextiles continue to provide practical and
economic solutions to a wide variety of engineering
problems including drainage, filtration, separation and
reinforcement. The objectives and findings presented in
2


this research thesis deal specifically with the
application of geotextiles as soil reinforcement elements
in earthen structures including slopes, walls, and
embankments.
Geotextile-reinforcements in slopes improve the
stability of the slope by increasing the tensile strength
within the soil mass. Geotextile-reinforcements also
improve compaction along the edges of the slope by
providing lateral confinement to the edges of each lift
of soil. Geotextiles can also improve slope stability by
acting as drainage materials in fine-grained embankment
soils (Tatsuoka and Yamauchi 1986).
Retaining walls constructed of geotextile-reinforced
soils exhibit many advantages over conventional gravity
or cantilever retaining walls. The geotextile-reinforced
retaining walls are remarkably stable and inherently
flexible allowing the walls to withstand large foundation
settlements without failure. Also, the excellent in
plane permeability characteristics of the geotextile-
reinforcement materials enhance the internal drainage of
the wall and accelerate the consolidation of low
permeability backfill soils. Geotextile-reinforced soil
walls are relatively low cost structures and the
3


reinforcement materials are resistant to corrosion and
bacterial action.
Geotextile-reinforcement of soils are also used in
constructing embankments over nonuniform foundations that
contain voids or lenses of soft clay or peat. The
functions performed by the geotextile-reinforcements
include transferring stresses away from weak zones,
assisting in soil arching and redistributing vertical
loads over a larger portion of the nonuniform foundation
(Bonaparte,- Holtz, and Giroud 1987). Geotextile-
reinforcements in the overlying embankment allow the
embankment to be constructed rapidly to final grade
without the additional time and cost associated with
staged construction or soft foundation displacement
(Holtz and Christopher 1984)..
When a geotextile material is used as reinforcement
in an earthen structure the designer must have some idea
of the tensile stresses and strains that the geotextile
must resist during the design life of the reinforced
structure. The geotextile's allowed values of stress and
strain (load-deformation properties) are determined by
laboratory testing. Ideally, the laboratory testing will
simulate actual operational conditions. However,
researchers have experienced varying success in
4


developing laboratory testing procedures that simulate
actual operational conditions, especially conditions of
soil confinement. This thesis presents a relatively
simple test method designed to measure the inherent load-
deformation properties of geotextiles under typical
operational conditions for geotexti'le-reinforced earthen
structures.
1.1 Problem Statement
Design computations or analyses of geotextile-
reinforced earthen structures requires representative
values, either measured or estimated, for the load-
deformation properties (strength and stiffness) of the
geotextile materials used. One must also consider how
the geotextile's load-deformation properties are affected
by the actual working conditions and in particular by
confining pressures resulting from overburden soils.
Hence, there is a need for a simple and reliable test
method that measures the load-deformation properties of
geotextiles subjected to confining pressures.
Many current laboratory test methods are inadequate
for determining the load-deformation properties of
geotextiles because they are either over simplified
resulting in unrealistic boundary conditions or they are
5


very complex resulting in measured results that are
difficult to interpret. The existing test methods are
particularly limited in their ability to simulate
conditions of soil confinement in typical geotextile-
reinforced earthen structures.
1.2 Research Objectives
The research objectives of this thesis were two-
fold. The first objective was to develop a simple and
reliable test method capable of measuring the intrinsic
load-deformation properties of a geotextile under
confinement conditions simulating the typical operational
conditions of the geotextile. The second objective was
to determine how the internal structure and polymer
composition of different geotextile materials affect
their load-deformation properties under conditions of
confinement.
1.3 Methods of Research
A laboratory test method designed to test
geotextiles under confined conditions simulating actual
working conditions was introduced in 1991 (Wu 1991; Ling,
Wu, and Tatsuoka 1992). The new test method, called the
Intrinsic Confined Test, used a rubber membrane and a
6


thin soil layer to apply confining pressures uniformly
over the entire surface of the geotextile specimen.
During the test, both the confining material and the
geotextile deform the same amount with no relative
displacement between them. The Intrinsic Confined Test
differs from most tests methods which hold the confining
soils stationary while the geotextile deforms during the
test. This creates an unrealistic condition in which
soil-geotextile slippage must occur in order for the
geotextile to deform.
The first Intrinsic Confined Tests were, performed by
enclosing a geotextile specimen inside two thin soil
layers. The entire soil-geotextile-soil assembly was
then enclosed inside a thin rubber membrane. Confining
pressure was simulated by applying a vacuum pressure to
the rubber membrane enclosing the soil layers. The test
method proved successful in measuring the intrinsic
properties of the geotextile by allowing the confining
soil to strain compatibly with the geotextile during the
test. A similar test was performed using only the rubber
membrane as the confining material and demonstrated that
the same conditions simulating soil confinement could be
obtained. It was then proposed that the Intrinsic
Confined Test method and the test apparatus be further
7


simplified by eliminating the soil layer and using only
the rubber membrane to simulate confined conditions. A
laboratory test apparatus and test method were developed
to perform the proposed Simplified Intrinsic Confined
Test. Tests were performed on several types of
geotextile materials to evaluate the effectiveness and
the reliability of the simplified test method.
1.4 Outline of Thesis
Chapter 2 of this thesis presents some background
information discussing geotextile load-deformation
measurements and the physical characteristics of
geotextiles that most influence their load-deformation
behavior. Chapter 2 also discusses two examples of the
geotextile testing methods currently used to determine
the load-deformation properties of geotextiles under
conditions of confinement. Chapter 3 presents a detailed
description of a simplified Intrinsic Confined Test
method designed to measure the true load-deformation
properties of geotextiles under confined conditions
simulating actual working conditions. Chapter 3 also
describes the test apparatus and explains the procedures
for preparing a geotextile specimen and performing the
simplified test. Chapter 4 discusses the test results
8


for a number of geotextile specimens tested using the
simplified Intrinsic Confined Test. Chapter 5 presents a
summary of the test results and develops some conclusions
based on the test data. Recommendations for further
testing using the simplified Intrinsic Confined Test
method are also addressed. Appendix A contains examples
of actual test data collected for the tests performed in
this research project.
9


2. Background
It has been established that geotextiles can exhibit
nonlinear load-deformation properties that are related to
the physical characteristics of the geotextile and the
operational conditions (Holtz and Christopher 1984) .
This chapter discusses the physical characteristics and
manufacturing processes that produce different geotextile
types with substantially different load-deformation
properties. Also discussed are the load-deformation
properties of geotextiles related to design and the
physical test conditions affecting the measured load-
deformation properties. The last section discusses
current geotextile testing methods.
2.1 Physical Characteristics
A geotextile's load-deformation properties are a
function of the physical characteristics of the
geotextile including the chemical composition of the
individual fibers and the internal structure of the
finished geotextile fabric.
Most geotextiles are composed of synthetic polymer
fibers. A variety of polymer types are used in
10


manufacturing geotextiles including polyester,
polypropylene, polyamide (Nylon), polyethylene, and
polyvinyl chloride (PVC). The geotextile materials
considered for this thesis were limited to polyester and
polypropylene materials, since they represent the
majority of the polymers used in geotextiles.
The internal structure of a geotextile is determined
by the manufacturing process. Geotextile manufacturing
involves three basic steps. The first step is the
chemical formation of the synthetic polymer. The second
step involves extrusion of polymers as either circular
filaments or flat tapes which become the individual
fibers of the geotextile. The third step converts the
individual fibers into a geotextile product by weaving,
knitting or bonding the fibers together to form a fabric
(Ingold and Miller 1988).
The finished fabric type (woven, non-woven or knit)
determines the internal structure of the geotextile which
in turn influences its load-deformation properties. Knit
fabrics are seldom used as geotextiles and are not
discussed in this thesis.
Woven fabrics, as the name implies, are formed by
weaving the fibers into a fabric (see Figure 2.1). In
comparing fabrics of similar composition and weight, the
11


woven geotextile fabrics are generally the stiffest and
strongest materials. It is important to note that the
load-deformation properties of woven materials are the
least affected by confining pressures.
Fig. 2.1 Woven fabric (Ingold and Miller 1988)
Non-woven fabrics are bonded together by mechanical,
thermal or chemical processes. The bonding process
largely determines the internal structure of the non-
woven geotextiles.
The mechanical bonding (or needle-punching) process
completes the fabric by using a conveyer to carry a mat
12


of individual fibers through rows of reciprocating barbed
needles which catch and tug on the fibers tangling them
together. The result is a needle-punched fabric having a
loose and very open internal structure (see Figure 2.2).
Fig. 2.2 Non.-woven needle-punched fabric (Ingold and
Miller 1988)
The thermal (or heat-bonding) process involves
passing the polymer fibers between heated rollers or
through a linear oven that bonds the fibers by fusion.
The result is a heat-bonded fabric having an internal
structure that is somewhat fixed and much less open when
compared to the needle-punched fabrics (see Figure 2.3).
13


Fig. 2.3 Non-woven heat-bonded fabric (Ingold and Miller
1988)
The chemical bonding (or resin-bonding) process
generally follows the mechanical bonding process, but
then adds a chemical binder to produce fabrics with
internal structures similar to the heat-bonded fabrics
(see Figure 2.4).
14


Fig. 2.4 Non-woven Chemical-bonded fabric (Ingold and
Miller 1988)
The non-woven fabrics generally have loose internal
structures, lower strengths and a lower tensile modulus
or stiffness. The non-woven materials are also often
pressure sensitive meaning they may be significantly
affected by confining pressures.
15


2.2 Load-De£ormation Properties
Design computations for soil-reinforcement
applications generally consider a geotextile's tensile
characteristics derived from a load-deformation curve
similar to the one shown in Figure 2.5. Tensile
characteristics derived from the load-deformation curve
generally include the ultimate tensile strength (Point F
on Figure 2.5), the initial stiffness or tensile modulus
(Slope of OA on Figure 2.5) and the secant stiffness or
secant modulus which is the geotextile's tensile
resistance at a given strain (Slope of OB on Figure 2.5).
STRAIN (%)
Fig. 2.5 Typical load-deformation curve
16


The maximum tensile strains that develop in
geotextile-reinforced earthen structures typically range
from 2 to 5 percent. These low strains are the strains
at which peak soil shear strengths are mobilized.
Therefore, the geotextile resistance at the same low
strain is used for design. However, when large-strain,
constant volume, soil strengths are used for the design,
the geotextile tensile resistance measured at strains
ranging from 5 to 10 percent is more appropriate
(Bonaparte, Holtz, and Giroud 1987). Note that the peak
strength of the geotextile is not used. Some highly
extensible geotextiles experience strains well over 100
percent without reaching their peak strength. Since it
is unlikely that the ultimate strength of the more
extensible geotextiles will ever be mobilized during
their design life, the stiffness or tensile modulus of
the geotextile at lower strains is more important for
design purposes.
The load-deformation properties measured in this
research include the tensile strength measured at failure
of the specimen and the tensile stiffness or secant
modulus measured at 5 and 10 percent strain in the
specimen.
17


The measured load-deformation properties of a
geotextile may be significantly affected by the external
physical test conditions present during testing.
Physical test conditions that must be considered for any
test include the specimen aspect ratio (width to length),
the temperature during the test and, in the case of
constant rate-of-strain tests, the strain rate applied to
the specimen during the test.
It can be demonstrated that lateral straining (neck
down) during geotextile testing is related to the shape
of the geotextile specimen and can affect the measured
tensile strength. The influence of specimen shape on the
measured strength is shown in Figure 2.6. It has been
suggested that an aspect ratio of 2 or more is adequate
to prevent the affects of lateral strain (McGown,
Andrawes, and Kabir 1982). An aspect ratio of 2 is also
specified for the Wide-Width Strip Test (ASTM D 4595-86)
which was intentionally designed to minimize the affects
of lateral strain and to provide a standard for
comparison between geotextiles (ASTM 1987b). However, It
has been demonstrated that some extensible needle-punched
geotextiles still display significant lateral straining
even with an aspect ratio of 2 It was also
demonstrated that the affects of confining pressures were
18


more pronounced on the geotextile specimens having an
aspect ratio of 2 as compared to larger aspect ratios
(Ling, Wu, and Tatsuoka 1992).
Fig. 2.6 Measured geotextile strengths for different
specimen aspect ratios (Myles 1987)
Therefore, to minimize the affects of lateral strain
and to simulate more representative operational
conditions, an aspect ratio of 6 was chosen for all tests
performed in this research.
Temperatures also affect the measured load-
deformation properties of geotextiles. The polymer
19


fibers in the geotextile materials are sensitive to heat.
When extreme temperatures are expected in the field, the
test conditions and/or results should be appropriately
adjusted. However, since geotextile strengths will
increase as temperatures decrease and since the
temperatures specified for most ASTM testing are above
the in-ground temperatures of most geotextile
applications, the testing results should be conservative
(Bonaparte, Holtz, and Giroud 1987).
In this research, temperatures and humidity were
recorded during each test performed to ensure that they
were not a factor in the measured load-deformation
properties.
The rate of strain during testing also affects the
measured load-deformation properties (see Figure 2:7).
The standard ASTM D4595 Wide-Width Test specifies a rate
of strain of 10% per minute during the test. Strain
rates much lower than 10% per minute are more
representative of actual working conditions since the
design life of earthen structures can be 50 years or
more. Also, as shown in Figure 2.7, lower rates of
strain result in lower measured strengths. Therefore, to
determine load-deformation properties that are more
representative of actual working conditions, the lowest
20


practical rates of strain are preferred for geotextile
testing.
The rate of strain for all tests conducted in this
research was 2% per minute. This selected rate was as
low as practical to provide more representative test
results, but still sufficient to allow the test durations
for the more extensible geotextiles to remain under one
hour.
o -]
0.3 -
-C
g
c
D
<5
a
£
O)
c
0
CO
0.6 -
0.4 -
0.2 -
0.0
0 5
I ---1-----------T~
10 15 20
Extension %
Fig. 2.7 Measured load-deformation properties for
different rates of strain (Myles 1987)
21


2.3 Geotextile Testing Methods
For discussion in this thesis geotextile testing
methods are grouped into two general types of tests,
index tests and property tests. Index tests provide test
data primarily for quality control and comparison
purposes. Initially index tests were adapted from the
textile industry. The data developed from the
conventional textile tests were not always suitable for
designing geotextile reinforced structures. For example,
tests designed to evaluate an elbow punching through a
shirt sleeve may not be representative of the punching
resistance of a geotextile subjected to large aggregate
dropped from a loaded dump truck (Holtz and Christopher
1984) Index tests provide only an indication of the
physical and mechanical properties of a geotextile.
Therefore, index test data used for design or analyses
must be used with caution because the measured properties
do not represent the true properties of the geotextile
operating under actual working conditions. Many of the
ASTM tests, such as ASTM D4632 (Grab Method) (ASTM 1987a)
and ASTM D4595 (Wide-Width Strip Method) (ASTM 1987b),
are index tests. These tests impose unusual or
unrealistic boundary conditions on the test specimen and
the test results are not representative of the material's
22


load-deformation properties under actual field
conditions. However, in the absence of other reliable
data, index test data has been commonly used in the
design of geotextile-reinforced earthen structures
Property tests,, unlike index tests, are designed to
measure the true load-deformation properties of
geotextiles subjected to test conditions simulating
actual field conditions. A variety of property tests
have been proposed, but few have gained acceptance. The
value of a property test depends upon how accurately the
method measures the load-deformation properties of a
geotextile subjected to test conditions simulating actual
working conditions.
2.3.1 Confined Test Methods
A number of researchers have developed test methods
for determining the confined, in-soil, load-deformation
properties of geotextiles (McGown, Andrawes, and Kabir
1982; El-Fermaoui and Nowatzki 1982; Christopher, Holtz,
and Bell 1986; Siel, Wu, and Chou 1987; Leshchinsky and
Field 1987; Kokkalis and Papacharisis 1989). Most of the
confined test methods hold the confining soil stationary
while the geotextile deforms under the applied load. The
result is relative movement or sliding at the interface
23


between the soil and the geotextile. The sliding induces
resistance forces in the confining materials which are
then measured in combination with the true or intrinsic
tensile strengths of the geotextile (Wu 1991). The
forced sliding results in measured load-deformation
properties which are difficult to interpret and may not
be representative of the actual load-deformation
properties intrinsic to the geotextile being tested.
Research and experience indicate that soils in a
reinforced soil structure deform "with" the geotextile
reinforcement and no sliding occurs at the soil-
geotextile interface until a near failure condition is
reached. If sliding does not occur, resistance forces in
the confining materials are not mobilized. Design
computations that assume geotextile strengths based on
the combined intrinsic geotextile strength and the
additional resistance forces can result in erroneously
high factors of safety and possibly unsafe designs (Wu
1991) Design computations will be more accurate if they
use the intrinsic geotextile strengths that do not
include additional resistance forces induced by sliding.
However, if sliding at the soil-geotextile interface
actually does occur and additional resistance forces are
24


mobilized, the design using the intrinsic geotextile
strengths alone will be conservative.
Test methods used to determine the confined load-
deformation properties of geotextiles can be divided into
two types. The first type includes methods modified from
the pullout test. The second type includes methods
modified from the triaxial extension test. The following
paragraphs describe one example of each type of test
method.
Figure 2.8 shows a simple test apparatus modified
from the pullout test. The apparatus is comprised of a
rigid test box with a tension loading mechanism. Soil
confinement is simulated by applying a normal load to the
rigid cap above the soil covering the geotextile
specimen. Test results derived from this test method
depend upon the sample size and the boundary conditions
imposed by the test apparatus.
25


Normal Load
Fig. 2.8 Test apparatus modified from pullout test (Wu
1991)
Note that the geotextile specimen is fixed to the
test box at one end and is allowed to move through a slot
at the other end. This allows larger strains at the free
end and nonuniform strains across the specimen. Also
note that the confining soil is held stationary in the
test box while the geotextile deforms during the test.
Relative movement between the geotextile and.the
confining soil causes sliding and induces shear forces at
the soil-geotextile interface.
26


As shown in Figure 2.9, the induced shear forces are
small at the fixed end and large at the free end. The
nonlinear distribution of the shear forces make it
difficult to interpret the test results. The nonuniform
stress distribution indicates that the measured results
of this test will depend upon both the size of the
specimen and the boundary conditions imposed by the test.
This type of test should not be considered a property
test.
Load
Fig. 2.9 Nonlinear distribution of shear forces (Wu
1991)
27


Figure 2.10 shows a more sophisticated apparatus
modified from the triaxial extension test. Soil
confinement is simulated using a rubber pressure bellows
inflated on two soil cakes covering each side of the
geotextile specimen. The method employs a number of
features designed to minimize the amount of load transfer
occurring between the specimen, the confining soil and
the testing apparatus. Even with the added features, the
test method may still develop additional nonlinear shear
forces. Note that both the specimen clamps' and the
reinforced ends of the geotextile are located inside the
rubber bellows and are acted upon by confining pressures.
The bellows appear to be transferring loads from the
lower specimen clamp through the test apparatus and back
into the upper specimen clamp. If shear stresses develop
at the interface between the geotextile and the confining
soil or between the confining soil and the pressure
bellows, the measured results will again depend on the
specimen size and will be difficult to interpret. Such
factors suggest that this type of test method is also
questionable as a property test.
28


mi mu. jiu
Confining Soil
Geotextile
Resin Treated Geotextile
Movable Clamp
Load Cell
i'
Load
Fixed Clamp
Pressure Bellow
I
Fig. 2.10 Test apparatus modified from triaxial extension
test (Wu 1991 modified from McGown, Andrawes, and Kabir
1982)
Figure 2.11 shows at test apparatus designed to
measure the intrinsic confined properties of a geotextile
specimen independent of the confining materials. The
test apparatus was designed to eliminate sliding and
prevent the development of nonuniform shear forces at the
interface between the geotextile and the confining
materials. The test apparatus also results in a uniform
application of confining pressures over the entire test
29


specimen, but not over the specimen clamps. The test
results derived from such an apparatus should be
representative of the geotextile's intrinsic load-
deformation properties under conditions simulating soil
confinement. Therefore, this test method is considered a
property test. The test method has been called the
Intrinsic Confined Test method.
30


TO LOADING MACHINE
UPPER ROD
CLAMP
MEMBRANE
SOIL
GEOTEXTILE
(UNREINFORCED ZONE)
GEOTEXTILE
(REINFORCED ZONE)
LOWER ROD
Fig. 2.11 Intrinsic Confined Test apparatus (Ling, Wu,
and Tatsuoka 1992)
31


3. Intrinsic Confined Test
The Intrinsic Confined Test method measures the
intrinsic confined load-deformation properties of
geotextiles required for the design and specification of
geotextiles materials used in reinforced soil structures.
The Intrinsic Confined Test method was first introduced
by Wu in 1991 (Wu 1991; Ling, Wu, and Tatsuoka 1992).
Initially, the tests were performed using a geotextile
specimen confined inside a thin soil layer and encased in
a rubber membrane. The entire assembly was then
subjected to tensile stress while a vacuum was applied to
the rubber membrane. The method allowed the soil to
deform with the geotextile in a compatible manner with no
sliding occurring at the soil-geotextile interface. Wu
then suggested that similar conditions of confinement and
strain compatibility could be achieved using only a thin
rubber membrane without soil as the confining material
(Wu 1991). Wu's suggestions would simplify the test
method and eliminate the corrections required to account
for the tensile resistance of the confining soil.
The curves shown in Figure 3.1 are the results of
tests performed using the Intrinsic Confined Test method.
32


Geotextile specimens having width-to-length ratios equal
to 8 were tested at constant, 2% per minute, strain
rates. The thin, layer of confining soil was a uniform
fine sand (Toyoura sand). A constant confining pressure
of 78.5 kN'/m2 was applied during the confined tests. The
load-deformation relationships shown in Figure 9 depict
non-woven spun-bonded polypropylene geotextile specimens
tested under three different conditions: confined in
soil, confined in rubber membrane, and unconfined (Ling,
Wu, and Tatsuoka 1992).
STRAIN (%)
Fig. 3.1 Load-deformation curves for a non-woven
geotextile (Ling, Wu, and Tatsuoka 1992)
33


The curves in Figure 3.1 indicate that application
of the confining pressures using either the thin soil
layer or the rubber membrane alone yields nearly the same
results. If one can demonstrate that reliable Intrinsic
Confined Test results are possible using only a rubber
membrane then the more simplified test method is
preferable.
3.1 Test Apparatus
Figure 3.2 shows the laboratory test apparatus
developed for the simplified test. The apparatus is
comprised of three parts, The constant rate tensile
testing machine, the fixed top and bottom bracket and the
removable specimen clamps. Figure 3.3 shows a schematic
of the brackets and specimen clamps. The fixed brackets
are attached to the testing machine and hold the specimen
clamps during the test. The specimen clamps firmly
secure the reinforced edges of the geotextile specimen.
The geotextile edges are reinforced with epoxy to improve
the clamping mechanism and to protect the internal
structure of the geotextile.
The brackets are constructed of steel and reinforced
with additional steel bars to maintain the applied force
in the axial direction and to prevent yielding in the
34


brackets while testing higher strength geotextiles. The
top bracket is fastened directly to the test machine by a
threaded connection at the top of the bracket. The
bottom bracket is attached to a larger bracket that fits
over the testing machine platen. Both top and bottom
brackets are shaped so the specimen' clamps can slide
inside the brackets and can be quickly and easily
installed or removed from the test machine.
Fig. 3.2 Simplified Intrinsic Confined Test apparatus
The specimen clamps are designed to hold any range
of geotextile specimen sizes with widths up to 300 mm.
35


The bolt holes in the clamps are evenly spaced at 25 mm
centers to provide a uniform clamping pressure along the
entire width of the geotextile specimen. The bolts are
recessed into the clamp to allow the clamps to sit
symmetrically in the brackets and in line with the axis
of the testing machine.

@@@ |
0 5 10cm
1 ... ... i ...... .1.. ... i i i !
Scotc
Fig. 3.3 Brackets and specimen clamps
36


3.2 Test Materials
The materials selected for testing included five
geotextiles of different structures and polymer, types.
One geotextile was a woven geotextile. The other four
were non-woven geotextiles, among which two were needle-
punched and two were heat-bonded. Selected index
properties of these geotextiles, as provided by the
manufacturers, are shown in Table 3.1.
Plane strain conditions typical of field
installation of geotextiles, were simulated using
specimens with a high aspect ratio (the ratio of width to
gage length). The aspect ratio required to achieve a
near-plane-strain condition is known to differ for
different geotextiles; however, an aspect ratio of
four(4) is generally considered adequate for most
geotextiles. Load-deformation testing using geotextile
specimens of small aspect ratio may result in significant
lateral retraction (i.e., "necking" due to Poisson .
effect), especially when the strains are large
(Christopher, Holtz, and Bell 1986; Siel, Wu, and Chou
1987).
Therefore, an aspect ratio of six(6) was chosen for
all specimens tested. Each geotextile specimen was cut
into a rectangular shape approximately 150 mm by 75 mm.
37


TABLE 3.1 Geotextile properties
Geotextile Properties Specimen A Specimen B Specimen C Specimen D Specimen E
Structure NW,NP NW,NP NW, HB ' NW,HB W
Polymer Type PES PES PP PP PP
Thickness,mm (ASTM D 1777-64) 2.4 3.2 0.30 0.38 0.51
Mass Per Unit Area,g/m2 (ASTM D 3776-84) 241 339 98 136 136
Grab Tensile/Elongation, kN/% (ASTM D 4632-86) 0.934/60 1.357/60 0.534/60 0.578/50 0.890/15
Wide Width Strength/Elongation Machine Direction, kN/m/% (ASTM D 4595-86) 17.1/65 26.8/74 NA NA 24.5/12
W = Woven PES = Polyester
NW = Nonwoven PP = Polypropylene
NP = Needle-punched
HB = Heat-bonded NA = Data not available


After application of the epoxy reinforcement, the
"deformable" area of the geotextile specimen (the area
not reinforced by the epoxy) was approximately 150 mm by
25 mm resulting in an aspect ratio of six.
The direction of deformation relative to the weave
or internal structure of the geotextile may also affect
the load-deformation properties of geotextiles. To
maintain a consistent direction of deformation in the
tests, the specimens were cut from the roll and prepared
so that each specimen was tested in their roll (machine)
direction.
3.3 Specimen Preparation
Preparation of test specimens involved the following
steps:
1. The geotextile was cut to the desired length and
width. The "length" direction was designated as the
direction of testing.
2. The geotextile specimen was reinforced along two
edges with a stiff epoxy (see Figure 3.4). The
epoxy performed several functions: it prevented
slippage or tearing of the geotextile within the
clamping mechanism; it fixed the internal structure
of the looser geotextile fabrics to prevent stress
39


concentrations; and it acted as a frame to hold the
. rubber membrane used to apply the confining
pressures. The thick epoxy reinforcement was formed
around the geotextile specimen using a mold
constructed from high density polyethylene (HDPE).
The mold was formed by two sheets of HDPE with the
desired shape of the mold cut out of the sheets (see
Figure 3.5a). The geotextile specimen was placed
between the two sheets of HDPE and the sheets were
clamped together onto a flat surface (see Figure
3.5b). The cut out shapes were filled with epoxy
and the specimen was left overnight to allow the
epoxy to completely cure. A 25 mm wide strip of
HDPE covering the area between the epoxy mold areas
defined the unreinforced "deformable" area of'the
geotextile and served to mask the area from the
epoxy.
3. After the epoxy reached full strength, the edges
were filed smooth.
4. Small diameter holes were drilled through the epoxy
to match the holes on the clamping mechanism.
40


EPOXY REINFORCEMENT AMD FRAME
rn
L.J
Scale
Fig. 3.4 Test specimen and epoxy reinforcement
41


Fig. 3.5a HDPE mold and prepared specimens
Fig. 3.5b Specimen preparation
42


3.4 Test Procedure
Performing the Intrinsic Confined Test method
involved the following steps:
1. A rubber membrane was stretched over the epoxy frame
enclosing the entire unreinforced area of the
geotextile (see Figure 3.6). The specimen was
bolted (through the holes in the epoxy) inside a
pair of metal specimen clamps. The specimen clamps
provide a seal at the top and bottom of the rubber
membrane along the entire width of the geotextile.
The 0.3 mm thick rubber membrane was cylinder shaped
and opened on both ends, the type used in
conventional triaxial soil testing. A length of
nylon tubing was used to attached the rubber
membrane to a vacuum pump which applied the vacuum
pressures (see Figure 3.7). The tubing was attached
to the pump using standard fittings and glued to the
rubber membrane at a flange on the end of the
tubing. The tubing flange was created by touching
the end of the tubing to a heated hot plate and then
quickly touching the melted end to a smooth surface.
The rubber membrane and nylon tubing assembly can be
used repeatedly, but care must be taken not to
43


damage the membrane while inserting and tightening
the bolts on the clamps.
Fig. 3.6 Stretching rubber membrane over specimen
2. The entire membrane-geotextile-membrane assembly was
attached to the top and bottom specimen clamps and
placed in a tensile testing machine by sliding the
clamps into the brackets which were securely
attached to the testing machine (see Figure 3.8).
44


Fig. 3.7 Rubber membrane and nylon tubing
Fig. 3.8 Brackets, specimen clamps and rubber membrane
45


3. A vacuum pump was connected to the nylon tubing and
a vacuum was applied to the membrane-geotextile-
membrane assembly.
4. The geotextile specimen was stressed in t.ension at a
constant rate of strain until failure occurred.
Throughout the test, the geotextile specimen was
subjected to uniform confining pressures by
maintaining a constant vacuum inside the rubber
membrane.
It should be noted that application of confining
pressures using a vacuum as described above limits the
available confining pressure to atmospheric pressure
(actually pressures lower than atmospheric are necessary
to ensure stable pressure application). Confining
pressures greater than atmospheric pressure may be
achieved using air or water pressure inside a chamber
similar to that used in a the triaxial test.
For the unconfined tests, the procedure was
identical to that of the confined test except that the
geotextile specimen was not subjected to pressure
confinement, i.e., Steps 1 and 3 were omitted.
An attempt was made to eliminate or hold constant
all other variables that could affect the test results.
Each test was performed with the same constant rate of
46


extension (CRE) type testing machine. The rate of
extension for each test was set at approximately 2
percent per minute. Constant confining pressures of
approximately 80 kN/m2 were maintained on the confined
test specimens by the vacuum applied to the rubber
membrane enclosing the geotextile specimen. Room
temperatures and humidity were recorded for each test to
determine if major fluctuations had occurred.
During each test the applied load and sample
extension were continuously recorded on the CRE testing
machine chart recorder. The data was then reduced to a
table format showing load per unit width of sample and
strain as a percent of initial sample length. The
tabulated data were then plotted showing the load-
deformation curve for each test. The load-deformation
curves were used to determine the modulus and the
strength of the tested specimen. Representative examples
of the CRE test machine recorded charts, reduced test
data and the plotted load-deformation curves are
presented in Appendix A.

47


4. Test Results and Discussion of Test Results
Load-deformation properties measured by the
Intrinsic Confined Test method were highly reproducible,
confirming results indicated by Wu in an earlier paper
published in the ASTM Geotechnical Testing Journal (Wu
1991). The load-deformation relationships for six tests
performed on Geotextile A are shown in Figure 4.1. Three
of the six tests were performed under confined conditions
and three were performed under unconfined conditions.
*- UNCONFINED TESTS -a- CONFINED TESTS
Fig. 4.1 Load-deformation curves for six tests on
geotextile A
48


Figure 4.2 shows the variations in confined load-
deformation properties for all five different geotextile
types tested. The curves representing the load-
deformation relationships form three distinct groups.
Each group was comprised of geotextiles with the same
manufacturing process and similar internal structures.
Variations within a group were explained by differences
in the geotextile thickness and mass per unit area (see
Table 3.1).
Fig. 4.2 Load-deformation curves for five different
geotextile types
49


Figures 4.3 through 4.7 show the load-deformation
relationships for each individual geotextile tested.
Each figure contains two curves representing typical test
results for confined and unconfined test conditions.
Table 4.1 shows average values for the secant
modulus at 5 and 10 percent strain -and the strength (at
failure) for the five geotextiles tested. The changes in
the load-deformation properties due to confinement ranged
from almost nil for geotextiles D and.E to a 67 percent
increase in stiffness for geotextile A.
4.1 Non-woven Needle-Punched Geotextiles
The non-woven, needle-punched, polyester
geotextiles, A and B, displayed the most significant
changes resulting from confinement (Table 4.1). The
needle-punched non-woven geotextiles shown in Figures 4.3
and 4.4 displayed a substantial increases in stiffness
(slope) at low strains. At strains above 10 percent the
curves became parallel indicating that the effects of
confinement were most significant at lower strains. The
confining pressures caused a 67 percent increase in the
stiffness and a 17 percent increase in the strength of
Geotextile A. The loose internal structure of the
needle-punched geotextile explains the dramatic results.
50


Geotextile B displayed a 33 percent increase in stiffness
and a 10 percent increase in strength due to confinement.
Geotextile B was of the same structure and polymer type
as Geotextile A, but Geotextile B was thicker and more
massive.
4.2 Non-woven Heat-Bonded Geotextiles
Figures 4.5 and 4.6 show confined and unconfined
curves for the heat-bonded non-woven geotextiles. The
non-woven, heat-bonded, polypropylene geotextiles, C and
D, showed little or no change in stiffness, but displayed
a slight increase in strength due to confinement (Table
4.1). It is to be noted that at smaller strains the
heat-bonded geotextiles exhibit little or no change in
stiffness due to confining pressures. However,, at larger
strains the measured strengths of the heat-bonded
geotextiles increased indicating that the affects of
confinement were more significant at higher strains.
Confinement of Geotextile C resulted in no significant
increase in the stiffness and a 23 percent increase in
the strength. Likewise, Geotextile D resulted in no
increase in stiffness and a 20 percent increase in
strength due to confinement. The lack of response to
confining pressures at small strains may be explained by
51


the internal structure of the geotextiles. The internal
structure of the heat-bonded geotextile was essentially-
confined by the manufacturing process and additional
confining pressures produced little change in the already
confined geotextile. However, at larger strains the
structure of the geotextile has become loosened and the
affects of confining pressures were more pronounced.
Also, similar to Geotextiles A and B, Geotextiles C and D
have the same polymer type and internal structure, but
Geotextile D was thicker, has more mass per unit area,
and shows less response to confinement pressures.
52


35
30-
-~ UNCONFINED TEST CONFINED TEST
Fig. 4.3 Load-deformation curve for non-woven needle-
punched Geotextile A
-At- UNCONFINED TEST -a- CONFINED TEST
Fig. 4.4 Load-deformation curve for non-woven needle-
punched Geotextile B
53


Fig. 4.5 Load-deformation curve for non-woven heat-
bonded Geotextile C
Fig. 4.6 Load-deformation curve for non-woven heat-
bonded Geotextile D
54


4.3 Woven Geotextile
The load-deformation relationships for the woven
geotextile are shown in Figure 4.7. No measurable change
in the load-deformation properties', due to confinement,
were observed for the woven geotextile tested. The small
decrease in stiffness observed for the confined condition
was believed to be more the result of variations in the
data than changes due to confinement.' The ultimate
strength values measured for these high strength woven
geotextiles were masked by failure occurring in the epoxy
and clamping mechanism. At strains greater than 15
percent individual fibers began to pull out of the epoxy
reinforcement masking the true load-deformation
properties of the geotextile (Table 4.1).
55


Fig. 4.7 Load-deformation curve for woven Geotextile E
56


TABLE 4.1 Summary of test data
Geotextile
Stiffness
(Sec. Mod. @ 5%)
(kN/m)
Stiffness
(Sec. Mod. @ 10%)
(kN/m)
Strength
(Load at failure)
(kN/m)
Non-woven
Needle-punched
Geotextile A
(Unconfined) 66 56 21.1
(Confined) 110 84 24.6
Geotextile B (Unconfined) 97 81 26.8
(Confined) 129 105 29.5
Non-woven Heat-bonded Geotextile C
(Unconfined) 48 34 7.0
(Confined) 51 37 8.6
Geotextile D (Unconfined) 66 47 9.2
(Confined) 65 49 11.0
Woven Geotextile E
(Unconfined) 188 161 21.7
(Confined) 171 153 20.0


4.4 Design Implications
For the design of geotextile-reinforced soil
structures using pressure-sensitive geotextiles, one must
ascertain the properties of the geotextile under
conditions simulating soil confinement. The load-
deformation properties of geotextiles, as affected by-
pressure confinement, may vary widely for different
geotextiles. It is to be noted that the magnitude of the
changes due to confining pressures, as revealed by the
results of.this study, are drastically less than the
values suggested by previous research. Tests performed
on non-woven needle-punched geotextiles, similar to
Geotextile A in this research, using similar confinement
pressures, strain rates and aspect ratios, resulted in
measured increases in the secant modulus at 5 percent
strain of 200 percent (McGown, Andrawes, and Kabir 1982;
Siel, Wu, and Chou 1987). Other tests performed using
various confining pressures, rates of strain and aspect
ratios indicated increases in the secant modulus at 5
percent strain ranging from 170 to 640 percent (El-
Fermaoui and Nowatzki 1982; Juran and Christopher 1989).
Test results obtained by confined test methods other than
the Intrinsic Confined Test do not allow the soil to
strain compatibly with the geotextile and thereby induce
58


shear resistance forces at the soil-geotextile interface
greatly, exaggerating the measured stiffness and strength
of the geotextile under typical operational conditions.
The Simplified Intrinsic Confined Test Method offers
a rational means of providing uniform specifications for
geotextile materials used in the design of earthen
structures. The Simplified Intrinsic Confined Test
provides the intrinsic stiffness and strength properties
of geotextiles independent of specimen size, boundary
conditions and confining materials. Therefore,
standardized parameters are available for design purposes
without the need of measuring and specifying the
properties of the expected confining soils, performing
complicated test procedures and interpreting complicated
test results.
59


5. Summary and Conclusions
5.1 Summary
A new test method, the Simplified Intrinsic Confined
Test, was developed to measure the intrinsic load-
deformation properties of geotextiles independent of
specimen sizes, boundary conditions and confining
materials. The test method simulates soil confinement
conditions, using vacuum pressures applied to a thin
rubber membrane. The method provides for compatible
strain between the geotextile specimen and the confining
membrane. The compatible strain eliminates the
development of shear forces in the confining materials
and provides for the measurement of the true load-
deformation properties of the geotextile alone.
The effectiveness of the simplified test method and
the affects of soil confinement on different geotextile
types were demonstrated by using the simplified test
method to test several geotextiles under both confined
and unconfined conditions. The utility of the simplified
test method, the load-deformation properties measured and
60


the design implications were analyzed and compared to
other currently used test methods.
5.2 Conclusions
The Simplified Intrinsic Confined Test method
provides an efficient and effective means of measuring
the intrinsic load-deformation properties of geotextiles
subjected to the predominant operational conditions
expected in geotextile-reinforced soil structures.
Results of the simplified tests were highly reproducible
and measured the intrinsic properties of the geotextile
materials alone, independent of specimen sizes, boundary
conditions or confining materials. Test methods other
than the Intrinsic Confined Test method include
additional shear resistance forces at the soil-geotextile
interface, thus greatly exaggerating the stiffness and
strength of the geotextile under typical operational
conditions. Therefore, the simplified test method is
superior to other confined test methods for the purposes
of developing more uniform design specifications and- for
analyzing reinforced earth structures where small
compatible strains between the confining soils and the
geotextile reinforcement materials are expected.
61


Test results using the Intrinsic Confined Test
method indicate that pressure confinement conditions
result in geotextile stiffness increases ranging from nil
to 67 percent and geotextile strength increases ranging
from nil to over 23 percent, depending upon the fabric
type and the internal structure of the geotextile.
However, because additional interface shear resistance
forces are eliminated, the increases in stiffness
measured in this research were still one third as large
as measured increases reported for other methods testing
similar materials under similar conditions.
The strength values for woven, polypropylene
geotextiles using the Intrinsic Confined Test, method were
limited to the bonding strength of the epoxy
reinforcement along the edges of the geotextile.
5.3 Recommendations for Further Study
Many geotextile-reinforced earth structures are
designed for long service lives. The long-term load-
deformation or creep properties of the geotextile
reinforcement in these structures is significant.
Depending on the type of geotextile and manufacturing
process, the tensile strength of a geotextile loaded to
failure over 50 years may be significantly less than the
62


strength of the same type of geotextile loaded to failure
over a few minutes.
In critical structures where the reinforcement is
expected to permanently resist large tensile loads, the
tensile resistance for design should be determined from
the results of creep tests rather than from the results
of short-term constant rate-of-strain tests. Unconfined
or in-isolation creep tests are acceptable for
geotextiles that are not strongly affected by soil
confinement. However, for pressure sensitive geotextiles
the unconfined tests will give conservative results.
Creep tests that simulate soil confinement, while more
difficult to carry out, will result in a more realistic
assessment of the in-ground, long-term, performance of
the structure (Bonaparte, Holtz, and Giroud 1987).
The Intrinsic Confined Test method is easily adapted
for performing long-term load-deformation testing on
pressure sensitive geotextiles. The creep tests would
follow the same Intrinsic Confined Test method using a
modified loading mechanism. The loading mechanism would
consist of a dead weight and hanger system. Test results
from a intrinsic confined creep tests would provide the
time-dependant load-deformation properties of
geotextiles.
63


APPENDIX A
Selected Test Data
64


65
.L^rO-\


TEST NUMBER: 21
DATE: 5/27/92
5.900 5.880
WIDTH (IN): 5.890
0.755 0.729
LENGTH (IN): 0.742
DEFORM LOAD
(IN) (LBS)
0 0
0.01 54
0.02 100
0.03 146
0.04 186
0.05 219
0.06 247
0.07 270
0.08 298
0.09 323
0.1 340
0.11 359
0.12 380
0.13 397
0.14 412
0.15 430
0.16 446
0.17 467
0.18 483
0.19 500
0.2 518
0.21 534
0.22 552
0.23 569
0.24 5B5
0.25 603
0.26 619
0.27 635
0.28 650
0.29 667
0.3 681
0.31 698
0.730 0.752
STRAIN STRESS
(%) (kN/m)
0.00 0.00
1.35 1.61
2.70 2.97
4.05 4.34 SEC.MOD@5%
5.39 5.53 103.64
6.74 6.51
8.09 7.34
9.44 8.03 SEC. MOD 10%
10.79 8.86 83.73
12.14 9.60
13.49 10.11
14.83 10.67
16.18 11.30
17.53 11.80
18.88 12.25
20.23 12.78
21.58 13.26
22.93 13.88
24.28 14.36
25.62 14.87
26.97 15.40
28.32 15.88
29.67 16.41
31.02 16.92
32.37 17.39
33.72 17.93
35.06 18.40
36.41 18.88
37.76 19.33
39.11 19.83
40.46 20.25
41.81 20.75
66


TEST NUMBER: 21
DATE: 5/27/92
5.900 5.880
WIDTH (IN): 5.890
0.755 0.729 0.730 0.752
LENGTH (IN): 0.742
DEFORM LOAD STRAIN- STRESS
(IN) (LBS) (%) (kN/m)
0.32 713 43.16 21.20
0.33 729 44.50 21.67
0.34 741 45.85 22.03
0.35 758 47.20 22.54
0.36 771 48.55 22.92
0.37 785 49.90 23.34
0.38 796 51.25 23.67
0.39 809 52.60 24.05
0.4 820 53.94 24.38
0.41 830 55.29 24.68
0.42 839 56.64 24.94
0.43 844 57.99 25.09
0.44 850 59.34 25.27
0.45 850 60.69 25.27
0.46 844 62.04 25.09
0.47 826 63.39 24.56
0.48 798 64.73 23.73
0.49 760 66.08 22.60
67


35
30
25
20
15
10
5
0
TEST-21
1 I I 1 I
10 20
I l i I I I I I I I--1--1--1--1--
30 40 50 60 70 80 90 1
STRAIN (%)


69


25
25 TEST NUMBER:
DATE: 6/4/92
: 152.650 152.000
WIDTH (IN): 5.997
: 24,250 24.250 24.350 24.750
LENGTH (IN): 0.961
DEFORM LOAD STRAIN STRESS
(IN) (LBS) (%) (kN/m)
0 0 0.00 0.00
0.01 70 1.04 2.04
0.02 140 2.08 4.09
0.03 196 3.12 5.72
0.04 250 4.16 7.30 SEC.MOD@5%
0.05 294 5.20 8.59 166.64
0.06 331 6.25 9.67
0.07 374 7.29 10.92
0.08 116 8.33 12.15
0.09 457 9.37 13.34 SEC.MOD@10%
0.1 491 10.41 14.34 140.71
0.11 527 11.45 15.39
0.12 561 12.49 16.38
0.13 587 13.53 17.14
0.14 602 14.57 17.58
0.15 619 15.61 18.08
0.16 639 16.66 18.66
0.17 658 17.70 19.21
0.18 676 18.74 19.74
0.19 690 19.78 20.15
0.2 699 20.82 20.41
0.21 705 21.86 20.59
0.22 712 22.90 20.79
0.23 716 23.94 20.91
70


LOAD (kN/m)
TEST-25


72


33 TEST NUMBER: 33
DATE: 6/15/92
151.900 151.950
WIDTH (IN): 5.981
LENGTH (IN):
21.200 20.850 21.250 21.850
0.838 DEFORM LOAD STRAIN STRESS
(IN) (LBS) (%) (kN/m)
0 0 0.00 0.00
0.01 34 1.19 ' 1.00
0.02 57 2.39 1.67
0.03 74 3.58 2.17
0.04 86 4.77 2.52 SEC.MOD@5%
0.05 96 5.97 2.81 51.47
0.06 103 7.16 3.02
0.07 108 8.35 3.16
0.08 117 9.55 3.43 SEC.MOD@10%
0.09 123 10.74 3.60 34.92
0.1 129 11.93 3.78
0.11 135 13.13 3.95
0.12 141 14.32 4.13
0.13 146 15.51 4.27
0.14 150 16.70 4.39
0.15 154 17.90 4.51
0.16 158 19.09 4.63
0.17 160 20.28 4.68
0.18 163 21.48 4.77
0.19 167 22.67 4.89
0.2 169 23.86 4.95
0.25 180 29.83 5.27
0.3 189 35.80 5.53
0.35 196 41.76 5.74
0.4 203 47.73 5.94
0.45 208 53.69 6.09
0.5 213 59.66 6.24
0.55 217 65.63 6.35
0.6 222 71.59 6.50
0.65 225 77.56 6.59
0.7 229 83.52 6.70
0.75 233 89.49 6.82
73


33
33 TEST NUMBER:
DATE: 6/15/92
151.900
WIDTH (IN): 5.981
21.200
LENGTH (IN): 0.838
DEFORM
(IN)
0.8
0.85
0.9
0.95
1
151.950
20.850 21.250 21.850
LOAD STRAIN STRESS
(LBS) (%) (kN/m)
236 95.46 6.91
239 101.42 7.00
243 107.39 7.11
246 113.35 7.20
248 119.32 7.26
74


15
10
5
0
TEST-33


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78