ASTM D3080/D3080M-23

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3080/D3080M − 23
Standard Test Method for
Direct Shear Test of Soils Under Consolidated Drained
Conditions
This standard is issued under the fixed designation D3080/D3080M; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* particles. Presently there is insufficient information available
for specifying the gap dimension based on particle size
1.1 This test method covers the determination of the con-
distribution.
solidated drained shear strength of one specimen of a soil
material under direct shear boundary conditions. The specimen
1.7 Units—The values stated in either inch-pound units or
is deformed at a controlled rate on or near a single shear plane
SI units [given in brackets] are to be regarded separately as
determined by the configuration of the apparatus.
standard. The values stated in each system may not be exact
equivalents; therefore, each system shall be used independently
1.2 Shear stresses and displacements are nonuniformly dis-
of the other. Combining values from the two systems may
tributed within the specimen. An appropriate height of the
result in nonconformance with the standard.
failure zone cannot be defined for calculation of shear strains.
Therefore, stress-strain relationships or any associated quantity
1.7.1 The gravitational system of inch-pound units is used
such as the shear modulus, cannot be determined from this test.
when dealing with inch-pound units. In this system, the pound
(lbf) represents a unit of force (weight), while the unit for mass
1.3 The results of the test are affected by the presence of
is a slug. The slug unit is not given, unless dynamic (F = ma)
coarse-grained soil or rock particles, or both, which may make
calculations are involved.
the testing data invalid in some cases. Check requirements of
1.7.2 It is common practice in the engineering/construction
maximum soil particle size in 6.2.1 and 6.2.2.
profession to concurrently use pounds to represent both a unit
1.4 Test conditions, including normal stress, access to water
of mass (lbm) and of force (lbf). This practice implicitly
during consolidation and shearing, and specimens conditions
combines two separate systems of units; the absolute and the
should be selected to represent the field conditions being
gravitational systems. It is scientifically undesirable to com-
investigated and are left to the engineer or office requesting the
bine the use of two separate sets of inch-pound units within a
test. The rate of shearing must be slow enough to ensure
single standard. As stated, this standard includes the gravita-
drained conditions.
tional system of inch-pound units and does not use/present the
1.5 Generally, three or more tests are performed on speci-
slug unit of mass. However, the use of balances and scales
mens from one soil sample, each under a different normal load, 3
recording pounds of mass (lbm) or recording density in lbm/ft
to determine the effects upon shear resistance and displace-
shall not be regarded as nonconformance with this standard.
ment. The development of criteria to interpret and evaluate test
1.8 All observed and calculated values shall conform to the
results is left to the engineer or office requesting the test.
guidelines for significant digits and rounding established in
Interpretation of multiple tests requires engineering judgment
Practice D6026, unless superseded by this test method.
and is beyond the scope of this test method. This test method
pertains to the requirements for a single test. 1.8.1 For purposes of comparing a measured or calculated
value(s) with specified limits, the measured or calculated
1.6 This test method limits the maximum particle size of the
value(s) shall be rounded to the nearest decimal of significant
test specimen based on the size of the shear box. Likewise, the
digits in the specified limit.
gap size during shear is specified. It is acceptable for the testing
1.8.2 The procedures used to specify how data are collected/
requester to require a certain gap size between the upper and
recorded and calculated in the standard are regarded as the
lower shear box halves to accommodate certain sand size
industry standard. In addition, they are representative of the
significant digits that generally should be retained. The proce-
dures used do not consider material variation, purpose for
This test method is under the jurisdiction of ASTM Committee D18 on Soil and
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
obtaining the data, special purpose studies, or any consider-
Compressibility of Soils.
ations for the user’s objectives; and it is common practice to
Current edition approved Nov. 1, 2023. Published December 2023. Originally
increase or reduce significant digits of reported data to be
approved in 1972. Last previous edition approved in 2011 as D3080/D3080M–11.
DOI: 10.1520/D3080_D3080M-23. commensurate with these considerations. It is beyond the scope
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3080/D3080M − 23
of these test methods to consider significant digits used in 3.1.1 For definitions of common technical terms used in this
analysis methods for engineering design. test method, refer to Terminology D653.
1.9 This standard does not purport to address all of the
3.2 Description of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 fabricated slurry specimen—laboratory reconstituted
responsibility of the user of this standard to establish appro-
specimen formed by consolidating a slurry to a specified water
priate safety, health, and environmental practices and deter-
content.
mine the applicability of regulatory limitations prior to use.
3.2.2 failure criterion—(Generically defined in Terminology
1.10 This international standard was developed in accor-
D653.) For this standard, failure criterion is often taken as the
dance with internationally recognized principles on standard-
maximum shear stress attained, or in the absence of a peak
ization established in the Decision on Principles for the
condition, the shear stress at 10 percent relative lateral dis-
Development of International Standards, Guides and Recom-
placement. Depending on soil behavior and field application,
mendations issued by the World Trade Organization Technical
other suitable criteria may be defined at the direction of the
Barriers to Trade (TBT) Committee.
requesting agency.
2. Referenced Documents
3.2.3 nominal normal stress—in the direct shear test, the
applied normal (vertical) force divided by the area of the shear
2.1 ASTM Standards:
box.
D653 Terminology Relating to Soil, Rock, and Contained
3.2.3.1 Discussion—The contact area of the specimen on the
Fluids
imposed shear plane decreases during shear and hence the true
D698 Test Methods for Laboratory Compaction Character-
normal stress is unknown.
istics of Soil Using Standard Effort (12,400 ft-lbf/ft (600
kN-m/m ))
3.2.4 nominal shear stress—in the direct shear test, the
D1557 Test Methods for Laboratory Compaction Character-
applied shear force divided by the area of the shear box.
istics of Soil Using Modified Effort (56,000 ft-lbf/ft
3.2.4.1 Discussion—The contact area of the specimen on the
(2,700 kN-m/m ))
imposed shear plane decreases during shear and hence the true
D1587/D1587M Practice for Thin-Walled Tube Sampling of
shear stress is unknown.
Fine-Grained Soils for Geotechnical Purposes
3.2.5 percent relative lateral displacement—The ratio, in
D2216 Test Methods for Laboratory Determination of Water
percent, of the relative lateral displacement to the diameter or
(Moisture) Content of Soil and Rock by Mass
lateral dimension of the specimen in the direction of shear.
D2435/D2435M Test Methods for One-Dimensional Con-
3.2.6 pre-shear—in strength testing, the stage of a test after
solidation Properties of Soils Using Incremental Loading
the specimen has stabilized under the consolidation loading
D2487 Practice for Classification of Soils for Engineering
condition and just prior to starting the shearing phase.
Purposes (Unified Soil Classification System)
D2488 Practice for Description and Identification of Soils 3.2.7 relative lateral displacement—the displacement be-
(Visual-Manual Procedures)
tween the top and bottom shear box halves.
D3740 Practice for Minimum Requirements for Agencies
Engaged in Testing and/or Inspection of Soil and Rock as
4. Summary of Test Method
Used in Engineering Design and Construction
4.1 This test method consists of placing the test specimen in
D4220/D4220M Practices for Preserving and Transporting
the direct shear device, applying a predetermined normal
Soil Samples (Withdrawn 2023)
stress, providing for wetting or draining of the test specimen, or
D4318 Test Methods for Liquid Limit, Plastic Limit, and
both, consolidating the specimen under the normal stress,
Plasticity Index of Soils
unlocking the shear box halves that hold the test specimen, and
D4753 Guide for Evaluating, Selecting, and Specifying Bal-
shearing the specimen by displacing one shear box half
ances and Standard Masses for Use in Soil, Rock, and
laterally with respect to the other at a constant rate of shearing
Construction Materials Testing
deformation while measuring the shearing force, relative lat-
D6026 Practice for Using Significant Digits and Data Re-
eral displacement, and normal displacement (Fig. 1). The
cords in Geotechnical Data
shearing rate must be slow enough to allow nearly complete
D6027/D6027M Practice for Calibrating Linear Displace-
dissipation of excess pore pressure.
ment Transducers for Geotechnical Purposes
D6913/D6913M Test Methods for Particle-Size Distribution
(Gradation) of Soils Using Sieve Analysis
3. Terminology
3.1 Definitions:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
The last approved version of this historical standard is referenced on
www.astm.org. FIG. 1 Test Specimen in Single Shear Apparatus
D3080/D3080M − 23
5. Significance and Use shear force to fail the specimen along a predetermined shear
plane (single shear) parallel to the faces of the specimen. The
5.1 The direct shear test is suited to the relatively rapid
frames that hold the specimen shall be sufficiently rigid to
determination of the drained friction angle of soils under
prevent distortion during shearing. The various parts of the
consolidated drained conditions because the drainage paths
shear device shall be made of material not subject to corrosion
through the test specimen are short, allowing excess pore
by moisture or substances within the soil, for example,
pressure to dissipate more rapidly than other drained strength
stainless steel, bronze, or aluminum, and the like. The use of
tests. It is applicable for testing intact, or reconstituted speci-
dissimilar metals, which may cause galvanic action, is not
mens. There is, however, a limitation on the maximum particle
permitted.
size (see 6.2.1 and 6.2.2).
6.2 Shear Box—A shear box, either circular or square, made
5.2 The testing protocols represent a field situation where
of stainless steel, bronze, or aluminum, with provisions for
complete consolidation has occurred under the existing normal
drainage through the top and bottom. The box is divided by a
stresses. Failure is reached slowly under drained conditions to
straight plane into two halves of equal thickness which are
allow excess pore pressure dissipation during shear. The shear
fitted together with alignment screws. The shear box is also
rate must meet the requirements of 9.10. The results from
fitted with gap screws, which create the space (gap) between
several tests may be used to express the relationship between
the top and bottom halves of the shear box prior to shear. The
normal stress on the failure plane and drained shear strength.
two halves shall provide a bearing surface for the specimen
NOTE 1—The equipment specified in this standard method is not
appropriate for performing undrained shear tests. Using a fast displace- along the shear plane during relative lateral displacement.
ment rate without proper control of the volume of the specimen will result
6.2.1 The minimum specimen diameter for circular
in partial drainage and incorrect measurements of shear parameters.
specimens, or width for square specimens, shall be 2.0 in.
5.3 During the direct shear test, there is rotation of principal
[50 mm], or not less than ten (10) times the maximum particle
stresses and failure may not occur on the weakest plane since
size diameter, whichever is larger.
failure is forced to occur on or near a plane through the middle
6.2.2 The minimum initial specimen height shall be 0.75 in.
of the specimen. The fixed location of the plane in the test can
[20 mm], and not less than six (6) times the maximum particle
be an advantage in determining the shear resistance along
diameter.
recognizable weak planes within the soil material and for
6.2.3 The minimum specimen diameter or width to height
testing interfaces between dissimilar materials.
ratio shall be 2.0 or greater.
NOTE 3—A light coating of grease applied to the inside of the shear box
5.4 There are some limitations of the test, such as nonuni-
may be used to reduce friction between the specimen and shear box.
formity of shear stress on the failure plane and possibilities of
TFE-fluorocarbon coating may also be used on these surfaces instead of
nonuniformity of the failure plane due to nonuniformities
grease to reduce friction.
within the soil and applied forces (moments caused by top half
6.3 Porous Inserts—Porous inserts function to allow drain-
of shear box movement either up or down during shearing, and
age from the soil specimen along the top and bottom bound-
the like). Furthermore, when testing intact stiff clays, which are
aries. They also function to transfer shear stress from the insert
highly overconsolidated, there might be fissures or other
to the top and bottom boundaries of the specimen. Porous
discontinuities to cause excessive tilting, vertical movement
inserts shall consist of silicon carbide, aluminum oxide, or
(up or down) while shearing, and the like, and which, would
metal which is not subject to corrosion by soil substances or
nullify the use of the direct shear test.
soil moisture. The proper grade of insert depends on the soil
5.5 The area of the shear surface decreases during the test.
being tested. The hydraulic conductivity of the porous insert
This area reduction creates uncertainty in the actual value of
shall be substantially greater than that of the soil, but shall be
the shear and normal stress on the shear plane but should not
textured fine enough to prevent excessive intrusion of the soil
affect the ratio of these stresses.
into the pores of the insert; see Note 4. The diameter or width
NOTE 2—The quality of the result produced by this standard is
of the top porous insert or plate shall be 0.01 to 0.02 in. [0.25
dependent on the competence of the personnel performing it, and the
to 0.5 mm] less than that of the inside of the shear box. The
suitability of the equipment and facilities used. Agencies that meet the
insert functions to transfer the shear stress to the soil and must
criteria of Practice D3740 are generally considered capable of competent
and objective testing/sampling/inspection/and the like. Users of this test be sufficiently coarse to develop interlock. Sandblasting or
method are cautioned that compliance with Practice D3740 does not in
tooling the insert may help, but the surface of the insert shall
itself assure reliable results. Reliable results depend on many factors;
not be so irregular as to cause substantial stress concentrations
Practice D3740 provides a means of evaluating some of those factors.
in the soil. Porous inserts shall be checked for clogging on a
regular basis.
6. Apparatus
NOTE 4—Exact criteria for porous insert texture and hydraulic conduc-
6.1 Shear Device—A device to hold the specimen securely
tivity have not been established. The inserts have to be porous enough to
between two porous inserts in such a way that torque is not
allow drainage and make sure water can flow into the specimen to remove
applied to the specimen. The shear device shall provide a
any capillary stresses within the test specimen. It is important that the
means of applying a normal stress to the faces of the specimen,
hydraulic conductivity of the porous insert is not reduced by the collection
for measuring change in height of the specimen, for permitting of soil particles in the pores of the insert. Storing the porous inserts in a
water filled container between uses will slow clogging. The inserts can be
drainage of water through the porous inserts at the top and
cleaned by flushing, boiling, or ultrasonic agitation.
bottom boundaries of the specimen, and for submerging the
specimen in water. The device shall be capable of applying a 6.4 Loading Devices:
D3080/D3080M − 23
6.4.1 Device for Applying the Normal Force—The normal coincident with applied shear force along a plane. The bowl
force is typically applied by dead weights, a lever loading yoke also serves as the container for the test water used to submerge
activated by dead weights (masses), a pneumatic force the specimen.
cylinder, or a screw-driven actuator. The device shall be
6.9 Controlled High Humidity Environment—If required,
capable of maintaining the normal force to within 61 percent
for preparing specimens, such that water content gain or loss
of the specified force. It should apply the load quickly without
during specimen preparation is minimized.
significantly exceeding the steady value. Dead weight systems
6.10 Test Water—Water is necessary to saturate the porous
shall be checked on a regular schedule to verify the mass of
inserts and fill the submersion reservoir. Ideally, this water
individual weights and the functionality of the lever mecha-
would be similar in composition to the specimen pore fluid.
nism. All systems with adjustable force application (for
Options include extracted pore water from the field, potable tap
example, pneumatic regulator or motor driven screw) require a
water, demineralized water, or saline water. The requesting
force indicating device such as a proving ring, load cell, or
agency should specify the water option. In the absence of a
pressure sensor.
specification, the test may be performed with potable tap water.
6.4.2 Device for Shearing the Specimen—The device shall
be capable of shearing the specimen at a uniform rate of
6.11 Trimmer or Cutting Ring, for trimming oversized
displacement, with less than 65 percent deviation. The rate to
samples to the inside dimensions of the shear box with a
be applied depends upon the consolidation characteristics of
minimum of disturbance. An exterior jig may be needed to
the test material as specified in 9.10. The rate is usually
maintain the shear box alignment during trimming.
maintained with an electric motor and gear box arrangement
6.12 Balances—A balance or scale conforming to the re-
and the shear force is determined by a force indicating device
quirements of Specification D4753 readable to 0.1 % or better.
such as a proving ring or load cell.
6.13 Apparatus for Determination of Water Content—As
NOTE 5—In order to test a wide range of soils the apparatus should
specified in Test Method D2216.
permit adjustment of the rate of displacement from 0.0001 to 0.04 in./min
[0.0025 to 1.0 mm/min].
6.14 Equipment for Compacting Specimens—If applicable,
NOTE 6—Shearing the test specimen at a rate greater than specified by
as specified in Test Methods D698 or D1557.
9.10 may produce partially drained shear results that will differ from the
drained strength of the material.
6.15 Miscellaneous Equipment—Including timing device
with a second hand, spatulas, knives, straightedge, wire saws,
6.4.3 Top Half of Shear Box—The weight of the top half of
and the like, used in preparing the specimen.
shear box supported by the specimen shall be less than 1
percent of the applied normal force during shear: this will most
likely require that the top shear box be supported by a counter 7. Test Specimen Preparation
force, the equipment modified, or the specimen will be sheared
7.1 Intact Specimens—Prepare intact specimens from large
under a greater applied normal force. In addition, the top half
intact samples or from samples secured in accordance with
of the shear box has to be supported in such a manner that it is
Practice D1587/D1587M, or other intact tube sampling proce-
free to move up and down during shearing without changing
dures. Intact samples shall be preserved and transported as
the normal stress on the shear plane greater than 1 percent of
outlined for Group C or D samples in Practice D4220/
the applied normal force.
D4220M. Handle specimens carefully to minimize disturbance,
6.5 Normal Force Measurement Device—A proving ring or changes in cross section, or loss of water content. If compres-
load cell (or calibrated pressure sensor when using a pneumatic sion or any type of noticeable disturbance would be caused by
loading system) accurate to 0.5 lbf [2.5 N], or 1 percent of the the extrusion device, split the sample tube lengthwise or cut off
normal force during shear, whichever is greater, is required a small section to facilitate removal of the sample with
when using anything but dead weights to apply the normal minimum disturbance. Prepare trimmed specimens, whenever
force. possible, in an environment which will minimize the gain or
loss of specimen moisture.
6.6 Shear Force Measurement Device—A proving ring or
7.1.1 The sample selected for testing shall be sufficiently
load cell accurate to 0.5 lbf [2.5 N], or 1 percent of the shear
large so that a test series can be prepared from similar material.
force at failure, whichever is greater.
While this standard test method applies to the measurements on
6.7 Deformation Indicators—Either dial gauges or displace-
one specimen, the requesting agency will typically specify a
ment transducers capable of measuring the change in the height
series of tests which cover a range of stress levels. The series
(normal displacement) of the specimen, with a readability of at
shall be performed on similar material.
least 0.0001 in. [0.002 mm] and to measure relative lateral
7.1.2 Extreme care shall be taken in preparing intact speci-
displacement with readability of at least 0.001 in. [0.025 mm].
mens of sensitive soils to prevent disturbance to the natural soil
D6027/D6027M provides details on the evaluation of displace-
structure.
ment transducers.
7.1.3 Assemble the shear box halves and determine the mass
6.8 Shear Box Bowl—A metallic box which supports the of the empty box. Trim the lateral dimensions of the specimen
shear box and provides either a reaction against which one half to fit snuggly into the shear box using either a shape cutting
of the shear box is restrained, or a solid base with provisions shoe or a miter box. With the specimen in the shear box, trim
for aligning one half of the shear box, which is free to move the top and bottom surface of the specimen to be flat and
D3080/D3080M − 23
parallel. Perform one or more water content determinations on 7.2.7 Apply incremental loads to achieve the desired speci-
material trimmed from the specimen in accordance with Test men height. Allow each load to remain until primary consoli-
Method D2216. dation has been achieved. The number and magnitude of
7.1.4 Determine and record the initial mass of the box plus individual loads will vary according to amount of vertical
specimen and height of the soil specimen for use in calculating movement required to achieve the desired height and therefore
the total density of the material. the desired water content. The final height shall be at least
NOTE 7—A controlled high-humidity room or laboratory glove box
60.01-in. [0.3-mm] of the desired height.
provides an appropriate atmosphere for trimming the specimen.
7.2.8 Remove the alignment screws and set the shear gap
7.2 Laboratory Fabricated Slurry Specimens—Shear testing using the gap screws and a feeler gauge to achieve a uniform
of fine-grained soils from reconstituted slurries are used, in gap.
part, to measure anticipated normally consolidated field con- 7.2.9 Proceed with shearing in accordance with 9.9 through
ditions where obtaining quality intact field samples proves 9.13.
difficult or not cost effective. Acquire enough material to
7.3 Reconstituted Specimens—Specimens shall be prepared
conduct the required series of tests. Air drying the specimen
using the compaction method, water content, and dry density
prior to disaggregation or sieving is allowed. Highly plastic
prescribed by the individual assigning the test. Specimens may
soils, tropical soils and organic soils shall not be air dried.
be molded by using either kneading or tamping method. One
Blend the material to produce a uniform slurry and if
layer of the soil is placed in the shear box and compacted/
necessary, divide into appropriate quantities for each required
reconstituted to a known volume by adjusting the number of
water content. Allow the moist material to stand prior to
tamps and the force per tamp to meet the initial specimen
specimen preparation in accordance with Table 1.
height. The top of each layer shall be scarified prior to the
7.2.1 Take a representative portion of the test batch for
addition of material for the next layer. The compacted layer
water content determination in accordance with D2216. After
boundaries shall be positioned so they are not coincident with
the water content specimen is secured, immediately place the
the shear plane defined by the shear box halves, unless this is
remainder of the test batch in a sealed container and store in a
the stated purpose for a particular test. The tamper used to
humidity room or moisture cabinet.
compact the material shall have an area in contact with the soil
7.2.2 Using the water content of the slurry and the lower
equal to or less than one-half the area or the shear box. Test
desired water content of the fabricated slurry specimen, deter-
specimens may also be prepared by compacting soil using the
mine the mass of the slurry that will result in a final height
procedures and equipment used to determine compaction
within the direct shear cavity such that the height of the
characteristics of soils (Test Methods D698 or D1557), and
specimen i
...