ASTM D3080-98
(Test Method)Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions
Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions
SCOPE
1.1 This test method covers the determination of the consolidated drained shear strength of a soil material in direct shear. The test is performed by deforming a specimen at a controlled strain rate on or near a single shear plane determined by the configuration of the apparatus. Generally, three or more specimens are tested, each under a different normal load, to determine the effects upon shear resistance and displacement, and strength properties such as Mohr strength envelopes.
1.2 Shear stresses and displacements are nonuniformly distributed within the specimen. An appropriate height cannot be defined for calculation of shear strains. Therefore, stress-strain relationships or any associated quantity such as modulus, cannot be determined from this test.
1.3 The determination of strength envelopes and the development of criteria to interpret and evaluate test results are left to the engineer or office requesting the test.
1.4 The results of the test may be affected by the presence of soil or rock particles, or both, (see Section 7).
1.5 Test conditions including normal stress and moisture environment are selected which represent the field conditions being investigated. The rate of shearing should be slow enough to ensure drained conditions.
1.6 The values stated in inch-pound units are to be regarded as the standard. Within this test method the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of each other.
1.7 This standard does not purport to address the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: D 3080 – 98
Standard Test Method for
Direct Shear Test of Soils Under Consolidated Drained
Conditions
This standard is issued under the fixed designation D 3080; 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 * D 653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.1 This test method covers the determination of the con-
D 698 Test Method for Laboratory Compaction Character-
solidated drained shear strength of a soil material in direct
istics of Soil Using Standard Effort (12 400 ft-lbf/ft)
shear. The test is performed by deforming a specimen at a
D 854 Test Method for Specific Gravity of Soils
controlled strain rate on or near a single shear plane determined
D 1557 Test Method for Laboratory Compaction Character-
by the configuration of the apparatus. Generally, three or more
istics of Soil Using Modified Effort (56 000 ft-lbf/ft)
specimens are tested, each under a different normal load, to
D 1587 Practice for Thin-Walled Geotechnical Tube Sam-
determine the effects upon shear resistance and displacement,
pling of Soils
and strength properties such as Mohr strength envelopes.
D 2216 Method for Laboratory Determination of Water
1.2 Shear stresses and displacements are nonuniformly dis-
(Moisture) Content of Soil and Rock
tributed within the specimen. An appropriate height cannot be
D 2435 Test Method for One Dimensional Consolidation
defined for calculation of shear strains. Therefore, stress-strain
Properties of Soils
relationships or any associated quantity such as modulus,
D 2487 Test Method for Classification of Soils for Engi-
cannot be determined from this test.
neering Purposes
1.3 The determination of strength envelopes and the devel-
D 2488 Practice for Description and Identification of Soils
opment of criteria to interpret and evaluate test results are left
(Visual-Manual Procedure)
to the engineer or office requesting the test.
D 3740 Practice for Minimum Requirements for Agencies
1.4 The results of the test may be affected by the presence of
Engaged in the Testing and/or Inspection of Soil and
soil or rock particles, or both, (see Section 7).
Rock
1.5 Test conditions including normal stress and moisture
D 4220 Practices for Preserving and Transporting Soil
environment are selected which represent the field conditions
Samples
being investigated. The rate of shearing should be slow enough
D 4318 Test Method for Liquid Limit, Plastic Limit, and
to ensure drained conditions.
Plasticity Index of Soils
1.6 The values stated in inch-pound units are to be regarded
D 4753 Specifications for Evaluating, Selecting, and Speci-
as the standard. Within this test method the SI units are shown
fying Balances and Scales for Use in Soil Rock and
in brackets. The values stated in each system are not exact
Construction Materials Testing
equivalents; therefore, each system must be used indepen-
dently of each other.
3. Terminology
1.7 This standard does not purport to address all of the
3.1 Definitions—For definitions of terms used in this test
safety concerns, if any, associated with its use. It is the
method, refer to Terminology D 653.
responsibility of the user of this standard to establish appro-
3.2 Description of Terms Specific to This Standard:
priate safety and health practices and determine the applica-
3.2.1 Relative Lateral Displacement—The horizontal dis-
bility of regulatory limitations prior to use.
placement of the top and bottom shear box halves.
2. Referenced Documents 3.2.2 Failure—The stress condition at failure for a test
specimen. Failure is often taken to correspond to the maximum
2.1 ASTM Standards:
shear stress attained, or the shear stress at 15 to 20 percent
D 422 Method for Particle-Size Analysis of Soils
relative lateral displacement. Depending on soil behavior and
field application, other suitable criteria may be defined.
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
and Rock and is the direct responsibility of Subcommittee D18.05 on Structural
4. Summary of Test Method
Properties of Soils.
Current edition approved Aug. 10, 1998. Published January 1999. Originally 4.1 This test method consists of placing the test specimen in
published as D 3080 – 72. Last previous edition D 3080 – 90.
the direct shear device, applying a predetermined normal
Annual Book of ASTM Standards, Vol 04.08.
*A Summary of Changes section appears at the end of this standard.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3080
testing depends on several factors; Practice D 3740 provides a means of
stress, providing for wetting or draining of the test specimen, or
evaluating some of these factors.
both, consolidating the specimen under the normal stress,
unlocking the frames that hold the test specimen, and displac-
6. Apparatus
ing one frame horizontally with respect to the other at a
6.1 Shear Device—A device to hold the specimen securely
constant rate of shearing deformation and measuring the
between two porous inserts in such a way that torque is not
shearing force and horizontal displacements as the specimen is
applied to the specimen. The shear device shall provide a
sheared (Fig. 1).
means of applying a normal stress to the faces of the specimen,
5. Significance and Use
for measuring change in thickness of the specimen, for
permitting drainage of water through the porous inserts at the
5.1 The direct shear test is suited to the relatively rapid
top and bottom boundaries of the specimen, and for submerg-
determination of consolidated drained strength properties be-
ing the specimen in water. The device shall be capable of
cause the drainage paths through the test specimen are short,
applying a shear force to the specimen in water. The device
thereby allowing excess pore pressure to be dissipated more
shall be capable of applying a shear force to the specimen
rapidly than with other drained stress tests. The test can be
along a predetermined shear plane (single shear) parallel to the
made on all soil materials and undisturbed, remolded or
faces of the specimen. The frames that hold the specimen shall
compacted materials. There is however, a limitation on maxi-
be sufficiently rigid to prevent their distortion during shearing.
mum particle size (see 7.2).
The various parts of the shear device shall be made of material
5.2 The test results are applicable to assessing strength in a
not subject to corrosion by moisture or substances within the
field situation where complete consolidation has occurred
soil, for example, stainless steel, bronze, or aluminum, etc.
under the existing normal stresses. Failure is reached slowly
Dissimilar metals, which may cause galvanic action, are not
under drained conditions so that excess pore pressures are
permitted.
dissipated. The results from several tests may be used to
6.2 Shear Box, a shear box, either circular or square, made
express the relationship between consolidation stress and
of stainless steel, bronze, or aluminum, with provisions for
drained shear strength.
drainage through the top and bottom. The box is divided
5.3 During the direct shear test, there is rotation of principal
vertically by a horizontal plane into two halves of equal
stresses, which may or may not model field conditions.
thickness which are fitted together with alignment screws. The
Moreover, failure may not occur on the weak plane since
shear box is also fitted with gap screws, which control the
failure is forced to occur on or near a horizontal plane at the
space (gap) between the top and bottom halves of the shear
middle of the specimen. The fixed location of the plane in the
box.
test can be an advantage in determining the shear resistance
6.3 Porous Inserts, Porous inserts function to allow drain-
along recognizable weak planes within the soil material and for
age from the soil specimen along the top and bottom bound-
testing interfaces between dissimilar materials.
aries. They also function to transfer horizontal shear stress
5.4 Shear stresses and displacements are nonuniformly dis-
from the insert to the top and bottom boundaries of the
tributed within the specimen, and an appropriate height is not
specimen. Porous inserts shall consist of silicon carbide,
defined for calculating shear strains or any associated engineer-
aluminum oxide, or metal which is not subject to corrosion by
ing quantity. The slow rate of displacement provides for
soil substances or soil moisture. The proper grade of insert
dissipation of excess pore pressures, but it also permits plastic
depends on the soil being tested. The permeability of the insert
flow of soft cohesive soils. Care should be taken to ensure that
should be substantially greater than that of the soil, but should
the testing conditions represent those conditions being inves-
be textured fine enough to prevent excessive intrusion of the
tigated.
soil into the pores of the insert. The diameter or width of the
5.5 The range in normal stresses, rate of shearing, and
top porous insert or plate shall be 0.01 to 0.02 in. (0.2 to 0.5
general test conditions should be selected to approximate the
mm) less than that of the inside of the ring. If the insert
specific soil conditions being investigated.
functions to transfer the horizontal stress to the soil, it must be
NOTE 1—Notwithstanding the statement on precision and bias con-
sufficiently coarse to develop interlock. Sandblasting or tooling
tained in this standard: The precision of this test method is dependent on
the insert may help, but the surface of the insert should not be
the competence of the personnel performing the test and the suitability of
so irregular as to cause substantial stress concentrations in the
the equipment and facilities used. Agencies which meet the criteria of
soil.
Practice D 3740 are generally considered capable of competent and
objective testing. Users of this test method are cautioned that compliance
NOTE 2—Exact criteria for insert texture and permeability have not
with Practice D 3740 does not in itself assure reliable testing. Reliable
been established. For normal soil testing, medium grade inserts with a
3 −4 −3
permeability of about 0.5 to 1.0 3 10 ft/yr (5.0 3 10 to 1.0 3 10
cm/s) are appropriate for testing silts and clays, and coarse grade inserts
with a permeability of about 0.5 to 1.0 3 10 ft/yr (0.05 to 0.10 cm/s) are
appropriate for sands. It is important that the permeability of the porous
insert is not reduced by the collection of soil particles in the pores of the
insert; hence frequent checking and cleaning (by flushing and boiling, or
by ultrasonic cleaning) are required to ensure the necessary permeability.
6.4 Loading Devices:
FIG. 1 Test Specimens in (a) Single and (b) Double Shear 6.4.1 Device for Applying and Measuring the Normal
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3080
Force—The normal force is applied by a lever loading yoke natural soil structure. Determine the initial mass of the wet
which is activated by dead weights (masses) or by a pneumatic specimen for use in calculating the initial water content and
loading device. The device shall be capable of maintaining the unit weight of the specimen.
normal force to within 61 percent of the specified force
7.2 The minimum specimen diameter for circular speci-
quickly without exceeding it.
mens, or width for square specimens, shall be 2.0 in. (50 mm),
6.4.2 Device for Shearing the Specimen—The device shall
or not less than 10 times the maximum particle size diameter,
be capable of shearing the specimen at a uniform rate of
whichever is larger, and conform to the width to thickness ratio
displacement, with less than 65 percent deviation, and should
specified in 7.4.
permit adjustment of the rate of displacement from 0.0001 to
7.3 The minimum initial specimen thickness shall be 0.5 in.
0.04 in./min (.0025 to 1.0 mm/min). The rate to be applied
(12 mm), but not less than six times the maximum particle
depends upon the consolidation characteristics of the soils (see
diameter.
9.12.1). The rate is usually maintained with an electric motor
7.4 The minimum specimen diameter to thickness or width
and gear box arrangement and the shear force is determined by
to thickness ratio shall be 2:1.
a load indicating device such as a proving ring or load cell.
NOTE 4—If large soil particles are found in the soil after testing, a
6.4.3 The weight of the top shear box should be less than 1
particle size analysis should be performed in accordance with Method
percent of the applied normal force: this may require that the
D 422 to confirm the visual observations, and the result should be
top shear box be modified and supported by counter force.
provided with the test report.
NOTE 3—Shearing the test specimen at a rate greater than specified may
7.5 Specimen Preparation:
produce partially drained shear results that will differ from the drained
7.5.1 Undisturbed Specimens—Prepare undisturbed speci-
strength of the material.
mens from large undisturbed samples or from samples secured
6.5 Shear Force Measurement Device—A proving ring or
in accordance with Practice D 1587, or other undisturbed tube
load cell accurate to 0.5 lbf (2.5 N), or 1 percent of the shear
sampling procedures. Undisturbed samples shall be preserved
force at failure, whichever is greater.
and transported as outlined for Group C or D samples in
6.6 Shear Box Bowl—A metallic box which supports the
Practice D 4220. Handle specimens carefully to minimize
shear box and provides either a reaction against which one half
disturbance, changes in cross section, or loss of water content.
of the shear box is restrained, or a solid base with provisions
If compression or any type of noticeable disturbance would be
for aligning one half of the shear box, which is free to move
caused by the extrusion device, split the sample tube length-
coincident with applied shear force in a horizontal plane.
wise or cut it off in small sections to facilitate removal of the
6.7 Controlled High Humidity Room, if required, for pre-
specimen with minimum disturbance. Prepare trimmed speci-
paring specimens, such that water content gain or loss during
mens, wheneve
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