ASTM D6243-98
(Test Method)Standard Test Method for Determining the Internal and Interface Shear Resistance of Geosynthetic Clay Liner by the Direct Shear Method
Standard Test Method for Determining the Internal and Interface Shear Resistance of Geosynthetic Clay Liner by the Direct Shear Method
SCOPE
1.1 This test method covers a procedure for determining the internal shear resistance of a Geosynthetic Clay Liner (GCL) or the interface shear resistance between the GCL and an adjacent material under a constant rate of displacement or constant stress.
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Designation:D6243–98
Standard Test Method for
Determining the Internal and Interface Shear Resistance of
Geosynthetic Clay Liner by the Direct Shear Method
This standard is issued under the fixed designation D 6243; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope solidated Drained Conditions
D 4354 Practice for Sampling of Geosynthetics for Testing
1.1 This test method covers a procedure for determining the
D 4439 Terminology for Geosynthetics
internalshearresistanceofaGeosyntheticClayLiner(GCL)or
D 5321 Test Method for Determining the Coefficient of Soil
the interface shear resistance between the GCLand an adjacent
and Geosynthetic or Geosynthetic and Geosynthetic Fric-
material under a constant rate of displacement or constant
tion by the Direct Shear Method
stress.
D 6072 Guide for Obtaining Samples of Geosynthetic Clay
1.2 This test method is intended to indicate the performance
Liners
of the selected specimen by attempting to model certain field
conditions.
3. Terminology
1.3 This test method is applicable to all GCLs. Remolded or
3.1 Definitions—For definitions of terms relating to soil and
undisturbed soil samples can be used in the test device.
rock, refer to Terminology D 653. For definitions of term
1.4 This test method is not suited for the development of
relating to GCLs, refer to Terminology D 4439.
exact stress-strain relationships within the test specimen due to
3.2 Definitions of Terms Specific to This Standard:
the nonuniform distribution of shearing forces and displace-
3.2.1 adhesion, c , n—the shearing resistance between two
a
ment.
unlike materials under zero normal stress.
1.5 The values stated in SI units are to be regarded as the
3.2.2 angle of friction, n—(angle of friction between solid
standard. The values given in parentheses are for information
bodies, °,) the angle whose tangent is the ratio between the
only.
limiting value of the shear stress that resists slippage between
1.6 This standard does not purport to address all of the
two solid bodies at rest with respect to each other and the
safety concerns, if any, associated with its use. It is the
normal stress across the contact surface.
responsibility of the user of this standard to establish appro-
3.2.2.1 Discussion—Limiting values may be at the peak
priate safety and health practices and determine the applica-
shear stress or at some other failure condition defined by the
bility of regulatory limitations prior to use.
user.
2. Referenced Documents 3.2.3 atmosphere for testing geosynthetics, n—air main-
tained at a relative humidity of between 50 and 70 % and
2.1 ASTM Standards:
temperature of 21 6 2°C (70 6 4°F).
D 653 Terminology Relating to Soil, Rock, and Contained
2 3.2.4 coeffıcient of friction, n—a constant proportionality
Fluids
factor relating normal stress and the corresponding critical
D 698 Test Method for Laboratory Compaction Character-
shear stress for a defined failure condition.
istics of Soil Using Standard Effort (12 400 ft lbf/ft (600
3 2
3.2.5 cohesion, c, n—the portion of the internal shear
kN-m/m ))
strength indicated by the term c, in Coulomb’s equation t =c
D 1557 Test Method for Laboratory Compaction Character-
+ s tan (f).
n
istics of Soil Using Modified Effort (56 000 ft/lbf/ft (2700
3 2
3.2.6 direct shear friction test, n—for GCLs, a procedure in
kN-m/m ))
which the internal GCL or the interface between a GCL and
D 2435 Test Method for One Dimensional Consolidation
any other surface, under a range of normal stresses specified by
Properties of Soils
the user, is stressed to failure by the relative movement of one
D 3080 Method for Direct Shear Test of Soils Under Con-
surface against the other.
3.2.7 GCL, n—a manufactured hydraulic barrier consisting
of clay bonded to a layer, or layers, of geosynthetic materials.
This test method is under the jurisdiction of ASTM Committee D-35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.04 on Geosyn-
thetic Clay Liners.
Current edition approved March 10, 1998. Published June 1998. Annual Book of ASTM Standards, Vol 04.13.
Annual Book of ASTM Standards, Vol 04.08. .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6243–98
4. Summary of Test Method 5.2.4 Information on precision between laboratories is in-
complete. In cases of dispute, comparative tests to determine
4.1 The shear resistance internal to the GCL or between a
whether a statistical bias exists between laboratories may be
GCL and adjacent material, or between any GCL combination
advisable.
selected by the user, is determined by placing the GCLand one
5.3 The test results can be used in the design of GCL
or more contact surfaces, such as soil, within a direct shear
applications, including but not limited to, the design of liners
box.Aconstant normal stress representative of field stresses is
and caps for landfills, cutoffs for dams, and other hydraulic
applied to the specimen, and a tangential (shear) force is
barriers.
applied to the apparatus so that one section of the box moves
in relation to the other section. The shear force is recorded as
6. Apparatus
a function of the horizontal displacement of the moving section
of the shear box.
6.1 Shear Device—A rigid device to hold the specimen
4.2 The test is performed for a minimum of three different securely and in such a manner that a uniform force without
normal stresses, selected by the user, to model appropriate field
torque can be applied to the specimen. The device consists of
conditions. The peak shear stresses, or shear stresses at some both a stationary and moving container, each of which is
post-peak displacement, or both, are plotted against the applied capable of containing dry or wet soil and are rigid enough to
normal stresses used for testing. The test data generally are
not distort during shearing of the specimen. The traveling
represented by a best fit straight line whose slope is the container must be placed on firm bearings and rack to ensure
coefficient of friction between the two materials where the
that the movement of the container is only in a direction
shearing occurred, or within the GCL. The y-intercept of the parallel to that of the applied shear force.
straight line is the cohesion intercept for internal shearing or
NOTE 3—The position of one of the containers should be adjustable in
adhesion intercept for interface shearing.
the normal direction to compensate for deformation of the GCL and
adjacent materials.
5. Significance and Use
6.1.1 Square or rectangular containers are recommended.
5.1 Theproceduredescribedinthistestmethodfortheshear
They should have a minimum dimension that is greater of 300
resistance for the GCL or the GCL interface is intended as a
mm(12in.),15timesthed ofthecoarsersoilusedinthetest,
performance test to provide the user with a set of design values
or a minimum of five times the maximum opening size (in
for the test conditions examined. The test specimens and
plan) of the geosynthetic tested. The depth of each container
conditions, including normal stresses, generally are selected by
should be 50 mm (2 in.) or six times the maximum particle size
the user.
of the coarser soil tested, whichever is greater.
5.2 This test method may be used for acceptance testing of
NOTE 4—The minimum container dimensions given in 6.1.1 are guide-
commercial shipments of GCLs, but caution is advised as
lines based on requirements for testing most combinations of GCLs and
outlined in 5.2.1.
adjacent materials. Containers smaller than those specified in 6.1.1 can be
5.2.1 The shear resistance can be expressed only in terms of
used if it can be shown that data generated by the smaller devices contain
actual test conditions (see Note 1 and Note 2). The determined
no bias from scale or edge effects when compared to the minimum size
value may be a function of the applied normal stress, material
devices specified in 6.1.1. The user should conduct comparative testing
characteristics, size of sample, moisture content, drainage
prior to the acceptance of data produced on smaller devices. For direct
shear testing involving soils, competent geotechnical review is recom-
conditions, displacement rate, magnitude of displacement, and
mended to evaluate the compatibility of the minimum and smaller direct
other parameters.
shear devices.
NOTE 1—In the case of acceptance testing requiring the use of soil, the
6.2 Normal Stress Loading Device, capable of applying and
user must furnish the soil sample, soil parameters, and direct shear test
maintaining a constant uniform normal stress on the specimen
parameters.
for the duration of the test. Careful control and accuracy
NOTE 2—Testing under this test method should be performed by
laboratories qualified in the direct shear testing of soils, especially since (62 %) of normal stress is important. Normal stress loading
the test results may be dependent on site-specific and test conditions.
devices include, but are not limited to, weights, pneumatic or
hydraulic bellows, or piston-applied stresses. For jacking
5.2.2 This test method measures the total resistance to shear
systems, the tilting of loading plates must be limited to less
within a GCL or between a GCL and adjacent material. Total
than 2° from horizontal during shearing.
shear resistance may be a combination of sliding, rolling,
interlocking of soil particles, or adjacent surfaces, and shear
NOTE 5—Due to the potential inaccuracies in the normal stress applied
strain, or a combination thereof, within the GCL specimen.
by some test devices, the operating range of normal stresses for a device
5.2.3 This test method does not distinguish between indi- should be limited to between 10 and 90 % of its calibrated range. If a
device is used outside this range, the report shall so state and give a
vidual mechanisms, which may be a function of the soil used,
discussion of the potential effect of uncertainties in normal stress on the
method of soil placement, normal and shear stresses applied,
measured results.
rate of horizontal displacement, and other factors. Every effort
should be made to identify, as closely as is practicable, the 6.3 Shear Force Loading Device, capable of applying a
sheared area and failure mode of the specimen. Care should be shearing force to the specimen at a constant rate of horizontal
taken, including close visual inspection of the specimen after displacement (strain controlled), or at a constant horizontal
testing, to ensure that the testing conditions are representative stress (stress controlled) in a direction parallel to the direction
of those being investigated. of travel of the soil container, or both.The rate of displacement
D6243–98
should be controlled to an accuracy of 610 % over a range of 6.6 Soil Preparation Equipment, for preparing or compact-
at least 6.35 mm/min (0.25 in./min) to 0.025 mm/min (0.001 ing bulk soil samples, as outlined in Test Methods D 698,
in./min). In a constant stress test, the horizontal stress shall be D 1557, or D 3080.
maintained to an accuracy of 62 % of the normal stress. The 6.7 Miscellaneous Equipment, as required for preparing
system must allow constant measurement and readout of the specimens. A timing device and equipment required for main-
applied shear force. An electronic load cell or proving ring taining saturation of the geosynthetic or soil samples, if
arrangement is generally used. The shear force loading device desired.
should be connected to the test apparatus in such a fashion that
7. GCL Sampling
the point of the load application to the traveling container is in
7.1 Lot Sample—Divide the product into lots, and for any
the plane of the shearing interface and remains the same for all
lot to be tested, take the lot sample as directed in Guide D 6072
tests.
(see Note 5 and Note 6).
6.4 Displacement Indicators,forprovidingcontinuousread-
7.2 Laboratory Sample—Consider the units in the lot
outofthehorizontalsheardisplacement,andifdesired,vertical
sample as the units in the laboratory sample for the lot to be
displacement of the specimen during the consolidation or shear
tested. For a laboratory sample, take a sample extending the
phase, or both. Dial indicators, or linear variable differential
full width of the GCL production unit and of sufficient length
transformers (LVDTs), capable of measuring a displacement of
so that the requirements of 7.3 can be met. Take a sample that
at least 75 mm (3 in.) for horizontal displacement and 25 mm
will exclude material from the outer edge.
(1 in.) for vertical displacement are recommended. The sensi-
7.3 Test Specimens—From each unit in the laboratory
tivity of displacement indicators should be at least 0.02 mm
sample, remove the required number of specimens as outlined
(0.001 in.) for measuring horizontal displacement.
in 7.3.1.
6.5 GCL Clamping Devices, required for fixing GCL speci-
7.3.1 Remove a minimum of three specimens for shearing
mens to the stationary section or container, the traveling
in a direction parallel to the machine, or roll, direction of the
container, or both, during shearing of the specimen. Clamps
laboratory sample and three specimens for shearing in a
shall not interfere with the shearing surfaces within the shear
direction parallel to the cross-machine (cross-roll) direction, if
box and must keep the GCL specimens flat during testing. Flat
required (see Note 7 and Note 8). The specimens should be
jaw-like clamping devices normally are sufficient for interface
slightlylargerthantheinsidedimensionsinalldirectionsofthe
testing. Where the internal shear resistance is to be measured,
soil container described in 6.1.1, and they should be of
rough (textured) surfaces must be used on the top and bottom
sufficient size to facilitate clamping. All specimens should be
of the GCL to cause internal shearing within the GCL. These
free of surface defects, etc., that are not typical of the
surfaces must permit flow of water into and out of the test
laboratorysample.Spacethespecimensalongadiagonalofthe
specimen. Work is still in progress to define the best type of
unit of the laboratory sample. Take no specimens nearer the
rough surfaces.
edge of the GCLproduction unit than ⁄10 the width of the unit.
6.5.1 Selection of the type of rough (textured) surface
should be based on the flowing criteria:
NOTE 7—Lots for GCLs usually are designated by the producer during
6.5.1.1 The gripping surface sho
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