ASTM D6528-17

Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Fine Grain Soils

SIGNIFICANCE AND USE
5.1 The shear strength of a specimen depends on the method of shearing, soil type, vertical consolidation stress, time of consolidation, rate of strain, and prior stress history of the soil.  
5.2 In this test, the shear strength is measured under constant volume conditions that are equivalent to undrained conditions for a saturated specimen; hence, the test is applicable to field conditions wherein soils have fully consolidated under one set of stresses, and then are subjected to changes in stress without time for further drainage to take place.  
5.3 The constant volume (undrained) strength is a function of stress conditions. In this test method, the strength is measured under plane strain conditions and the principle stresses continuously rotate due to the application of shear stress. This simple shear stress condition occurs in many field situations including zones below a long embankment and around axially loaded piles.  
5.4 The state of stress within the simple shear specimen is not sufficiently defined nor uniform enough to allow rigorous interpretation of the results. Expressing the data in terms of the shear stress and vertical effective stress on the horizontal plane is useful for engineering purposes, but should not be confused with the effective stress parameters derived from other shear tests having better defined states of stress.  
5.5 The values of the secant shear modulus can be used to estimate the initial settlements of embankments built on saturated cohesive soils due to undrained shear deformations.  
5.6 The data and the rate of consolidation from the consolidation portion of this test are comparable to results obtained using Test Methods D2435 provided that the more rigorous consolidation procedure of Test Methods D2435 is followed.  
5.6.1 When using wire reinforced membranes the vertical displacements measured from Test Methods D2435 are somewhat smaller than for the direct simple shear test because the direct simple shear (DSS) speci...
SCOPE
1.1 This test method defines equipment specifications and testing procedures for the measurement of constant volume strength and stress-strain characteristics of cohesive soils after one-dimensional consolidation using a constant rate of simple shear deformation mode of loading. The constant volume condition is equivalent to the undrained condition for saturated specimens.  
1.2 This test method is written specifically for devices that test rectangular parallelepiped or cylindrical specimens. Other more general devices, such as the torsional shear hollow cylinder, may be used to perform consolidated constant volume simple shear tests but are beyond the scope of this test method.  
1.3 This test method is applicable to testing intact, laboratory reconstituted, and compacted soils, however, it does not include specific guidance for reconstituting or compacting test specimens.  
1.4 It shall be the responsibility of the agency requesting this test to specify the magnitude of the vertical consolidation stress prior to constant volume shear and, when appropriate, the maximum vertical consolidation stress, which will result in an overconsolidated specimen.  
1.5 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.  
1.5.1 In the engineering profession it is customary practice to use, interchangeably, units representing both mass and force, unless dynamic calculations (F=Ma) are involved. This implicitly combines two separate systems of units, that is, the absolute system and the gravimetric system. It is scientifically undesirable to combine two separate systems within a single standard. This test method has been written using SI units; however, inch-pound conversions are given in the gravimetric system, where the pound (lbf) represe...

General Information

• Status: Published
• Publication Date: 31-Jul-2017
• ICS: 13.080.20 - Physical properties of soils
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.05 - Strength and Compressibility of Soils

Relations

• Replaces: ASTM D6528-07 - Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Cohesive Soils (Withdrawn 2016)
• Effective Date: 01-Aug-2017
• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D854-23 - Standard Test Methods for Specific Gravity of Soil Solids by the Water Displacement Method
• Effective Date: 01-Nov-2023
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D2487-17 - Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
• Effective Date: 15-Dec-2017
• Refers: ASTM D2487-17e1 - Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
• Effective Date: 15-Dec-2017
• Refers: ASTM D2488-17 - Standard Practice for Description and Identification of Soils (Visual-Manual Procedures)
• Effective Date: 15-Jul-2017
• Refers: ASTM D4318-17 - Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
• Effective Date: 01-Jun-2017
• Refers: ASTM D4318-17e1 - Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
• Effective Date: 01-Jun-2017
• Refers: ASTM D7928-16e1 - Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
• Effective Date: 01-May-2016
• Refers: ASTM D7928-16 - Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
• Effective Date: 01-May-2016
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D1587-08(2012)e1 - Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes
• Effective Date: 15-May-2012
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012

Overview

ASTM D6528-17 is the Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Fine Grain Soils, established by ASTM International. This method outlines standardized procedures and equipment specifications for measuring the constant volume strength and stress-strain characteristics of cohesive soils after one-dimensional consolidation. The test simulates undrained field conditions, where soils are fully consolidated under an initial set of stresses and then subjected to rapid loading without further drainage. This standard is essential for geotechnical engineers and professionals working in soil mechanics, embankment design, and foundation analysis.

Key Topics

• Test Scope and Conditions:
  The method applies to intact, laboratory reconstituted, and compacted fine-grained soil specimens using devices designed for rectangular parallelepiped or cylindrical shapes.

• Constant Volume & Shear Strength Measurement:
  Shear strength is determined under constant volume (undrained) conditions, measuring soil response under plane strain, which reflects many real-world loading scenarios.

• Equipment and Apparatus:
  Requirements cover loading devices, displacement indicators, force transducers, vertical loading rams, shear slide tables, and lateral confinement systems, ensuring reliable and repeatable results.

• Calibration and Measurement:
  The procedure emphasizes accurate calibration and correction of apparatus compressibility and friction effects for vertical and shear force measurements.

• Significance for Engineering Practice:
  The derived shear strength and secant shear modulus inform key design parameters, including the estimation of initial settlements for embankments and analysis of soil behavior under rapid loading.

Applications

ASTM D6528-17 is vital in several geotechnical engineering applications:

• Foundation and Embankment Design:
  The test results help estimate the undrained shear strength and deformation characteristics of fine-grained soils, contributing to the safety and stability assessment of foundations and embankments, particularly those subjected to rapid loading.

• Assessment of Load-Bearing Capacity:
  The procedure is used to assess strength conditions for sites where cohesive soils experience stress changes without sufficient time for pore water dissipation.

• Predicting Settlement:
  The secant shear modulus values obtained aid in estimating the initial settlement of embankments built on saturated cohesive soils, supporting optimized structural design.

• Comparison with Other Soil Tests:
  Data from the consolidation phase of ASTM D6528-17 can be correlated with results from one-dimensional consolidation tests (ASTM D2435), providing validation and cross-comparison for comprehensive site investigation reports.

• Slope Stability and Pile Design:
  This test method simulates stress paths found in zones beneath embankments and near axially loaded piles, making it relevant for slope stability analysis and pile foundation projects.

Related Standards

Several other ASTM standards complement and enhance the application of ASTM D6528-17:

• ASTM D653: Terminology relating to soil, rock, and contained fluids.
• ASTM D2435: Test methods for one-dimensional consolidation properties of soils.
• ASTM D2216: Methods for laboratory determination of water (moisture) content of soil and rock.
• ASTM D1587: Practice for thin-walled tube sampling of fine-grained soils.
• ASTM D4318: Test methods for liquid limit, plastic limit, and plasticity index of soils.
• ASTM D6913: Test methods for particle-size distribution (gradation) of soils using sieve analysis.
• ASTM D7928: Test methods for particle-size distribution of fine-grained soils using hydrometer analysis.

These referenced standards provide definitions, sampling practices, index property determination, and test procedures that ensure the precision, reliability, and comparability of direct simple shear test results across different laboratories and field projects.

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By following ASTM D6528-17, professionals ensure accurate, repeatable, and standardized assessment of fine-grained soil strength and deformation under consolidated undrained direct simple shear conditions, supporting safer and more effective geotechnical engineering solutions.

Standards Content (Sample)

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: D6528 − 17
Standard Test Method for
Consolidated Undrained Direct Simple Shear Testing of Fine
Grain Soils
This standard is issued under the fixed designation D6528; 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* system, where the pound (lbf) represents a unit of force
(weight). The use of balances or scales recording pounds of
1.1 This test method defines equipment specifications and
mass (lbm), or the recording of density in lb/ft should not be
testing procedures for the measurement of constant volume
regarded as nonconformance with this test method.
strength and stress-strain characteristics of cohesive soils after
one-dimensional consolidation using a constant rate of simple 1.6 All observed and calculated values shall conform to the
shear deformation mode of loading. The constant volume guidelines for significant digits and rounding established in
condition is equivalent to the undrained condition for saturated Practice D6026.
specimens. 1.6.1 Theproceduresusedtospecifyhowdataarecollected/
recorded or calculated in this test standard are regarded as the
1.2 This test method is written specifically for devices that
industry standard. In addition, they are representative of the
test rectangular parallelepiped or cylindrical specimens. Other
significant digits that should generally be retained. The proce-
more general devices, such as the torsional shear hollow
dures used do not consider material variation, purpose for
cylinder,maybeusedtoperformconsolidatedconstantvolume
obtaining the data, special purpose studies, or any consider-
simple shear tests but are beyond the scope of this test method.
ations for the user’s objectives; it is common practice to
1.3 This test method is applicable to testing intact, labora-
increase or reduce significant digits of reported data to be
tory reconstituted, and compacted soils, however, it does not
commensuratewiththeseconsiderations.Itisbeyondthescope
include specific guidance for reconstituting or compacting test
of this test standard to consider significant digits used in
specimens.
analysis methods for engineering design.
1.4 It shall be the responsibility of the agency requesting 1.6.2 Measurements made to more significant digits or
better sensitivity than specified in this standard shall not be
this test to specify the magnitude of the vertical consolidation
regarded a nonconformance with this standard.
stress prior to constant volume shear and, when appropriate,
the maximum vertical consolidation stress, which will result in
1.7 This standard does not purport to address all of the
an overconsolidated specimen.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.5 Units—The values stated in SI units are to be regarded
priate safety, health, and environmental practices and deter-
as the standard. No other units of measurement are included in
mine the applicability of regulatory limitations prior to use.
this standard. Reporting of test results in units other than SI
1.8 This international standard was developed in accor-
shall not be regarded as nonconformance with this test method.
dance with internationally recognized principles on standard-
1.5.1 In the engineering profession it is customary practice
ization established in the Decision on Principles for the
touse,interchangeably,unitsrepresentingbothmassandforce,
Development of International Standards, Guides and Recom-
unless dynamic calculations (F=Ma) are involved.This implic-
mendations issued by the World Trade Organization Technical
itly combines two separate systems of units, that is, the
Barriers to Trade (TBT) Committee.
absolute system and the gravimetric system. It is scientifically
undesirable to combine two separate systems within a single
2. Referenced Documents
standard. This test method has been written using SI units;
however, inch-pound conversions are given in the gravimetric 2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
Compressibility of Soils. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2017. Published September 2017. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approvedin2000.Lastpreviouseditionapprovedin2007asD6528–07,whichwas Standards volume information, refer to the standard’s Document Summary page on
withdrawn January 2016 and reinstated in August 2017. DOI: 10.1520/D6528-17. the ASTM website.
*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
D6528 − 17
D854 Test Methods for Specific Gravity of Soil Solids by one cycle of secondary compression or one day longer than the
Water Pycnometer end of excess pore water pressure dissipation.
D1587 Practice for Thin-Walled Tube Sampling of Fine-
4.3 The specimen is sheared by displacing one platen
Grained Soils for Geotechnical Purposes
tangentially relative to the other at a constant rate of displace-
D2216 Test Methods for Laboratory Determination of Water
ment and measuring the resulting shear force. The platens are
(Moisture) Content of Soil and Rock by Mass
constrained against rotation and vertical movement throughout
D2435 Test Methods for One-Dimensional Consolidation
shear.
Properties of Soils Using Incremental Loading
D2487 Practice for Classification of Soils for Engineering
4.4 The specimen volume is held constant during shear to
Purposes (Unified Soil Classification System)
simulateundrainedconditions.Constantvolumeisachievedby
D2488 Practice for Description and Identification of Soils
changing the vertical load applied to the specimen to maintain
(Visual-Manual Procedures)
constant specimen height. Since the pore pressure is zero
D3550 Practice for Thick Wall, Ring-Lined, Split Barrel,
through shear, the change in vertical stress is equal to the
Drive Sampling of Soils
change in effective stress and assumed to be equal to the
D3740 Practice for Minimum Requirements for Agencies
change in pore water pressure that would occur in a sealed
Engaged in Testing and/or Inspection of Soil and Rock as
specimen confined by a constant vertical total stress.
Used in Engineering Design and Construction
NOTE 1—The quality of the result produced by this test standard is
D4220 Practices for Preserving and Transporting Soil
dependent on the competence of the personnel performing it, and the
Samples
suitability of the equipment and facilities. Agencies that meet the criteria
D4318 Test Methods for Liquid Limit, Plastic Limit, and
of Practice D3740 generally are considered capable of competent and
Plasticity Index of Soils
objective testing/sampling/inspection/etc. Users of this test standard are
D4452 Practice for X-Ray Radiography of Soil Samples cautioned that compliance with Practice D3740 does not in itself assure
reliable results. Reliable results depend on many factors; Practice D3740
D6026 Practice for Using Significant Digits in Geotechnical
provides a means of evaluating some of those factors.
Data
D6913 Test Methods for Particle-Size Distribution (Grada-
5. Significance and Use
tion) of Soils Using Sieve Analysis
D7928 Test Method for Particle-Size Distribution (Grada-
5.1 Theshearstrengthofaspecimendependsonthemethod
tion) of Fine-Grained Soils Using the Sedimentation
of shearing, soil type, vertical consolidation stress, time of
(Hydrometer) Analysis
consolidation, rate of strain, and prior stress history of the soil.
5.2 In this test, the shear strength is measured under
3. Terminology
constant volume conditions that are equivalent to undrained
3.1 Definitions:
conditions for a saturated specimen; hence, the test is appli-
3.1.1 For definitions of common technical terms used in this
cable to field conditions wherein soils have fully consolidated
standard, refer to Terminology D653.
under one set of stresses, and then are subjected to changes in
3.2 shear modulus, n—a measure of a material’s resistance
stress without time for further drainage to take place.
to shear stress, equal to the ratio of the increment in the shear
5.3 The constant volume (undrained) strength is a function
stress to the resultant increment in angle of deformation
of stress conditions. In this test method, the strength is
expressed in radians; also known as the modulus of rigidity.
measured under plane strain conditions and the principle
3.3 Definitions of Terms Specific to This Standard:
stresses continuously rotate due to the application of shear
3.3.1 active height control, n—a method of keeping the
stress. This simple shear stress condition occurs in many field
height of the specimen constant during the shearing process in
situations including zones below a long embankment and
which the displacement control mechanism is physically ad-
around axially loaded piles.
justed in response to the vertical displacement measurement.
5.4 The state of stress within the simple shear specimen is
3.3.2 passive height control, n—a method of keeping the
not sufficiently defined nor uniform enough to allow rigorous
height of the specimen constant during the shearing process in
interpretation of the results. Expressing the data in terms of the
which the specimen and force measuring device are clamped
shear stress and vertical effective stress on the horizontal plane
by a mechanism that is much stiffer than the specimen.
is useful for engineering purposes, but should not be confused
with the effective stress parameters derived from other shear
4. Summary of Test Method
tests having better defined states of stress.
4.1 In this test method a specimen of cohesive soil is
5.5 The values of the secant shear modulus can be used to
constrained vertically between two parallel, rigid platens and
estimate the initial settlements of embankments built on
laterally, such that the cross sectional area remains constant.
saturated cohesive soils due to undrained shear deformations.
4.2 The specimen is loaded vertically and allowed to con-
solidate one-dimensionally. Each vertical load increment is 5.6 The data and the rate of consolidation from the consoli-
maintained until excess pore water pressures are essentially dation portion of this test are comparable to results obtained
dissipated as interpreted from the vertical displacement rate. using Test Methods D2435 provided that the more rigorous
The maximum vertical load is maintained until completion of consolidation procedure of Test Methods D2435 is followed.
D6528 − 17
5.6.1 When using wire reinforced membranes the vertical using passive height control, the compressibility of the vertical
displacements measured from Test Methods D2435 are some- transducer plus compressibility of slide table must satisfy the
what smaller than for the direct simple shear test because the deflection requirement of 6.9.
direct simple shear (DSS) specimen’s lateral confinement is
6.5 Vertical Loading Ram—Asuitable device that must hold
less rigid.
one platen parallel to the other while allowing vertical dis-
5.6.2 The estimated preconsolidation pressure is compa-
placement of the specimen. If the piston resists the shear force,
rable provided the specimen is loaded sufficiently into the
it must do so with negligible rotation of the platen.
normally consolidated range.
6.6 Shear Slide Table—Asuitable device that must hold the
6. Apparatus
platens parallel to each other and allow shear displacement of
the specimen. When using passive height control device the
6.1 Fig. 1 presents a schematic diagram of the necessary
slidetable’scompressibilityplusthecompressibilityofvertical
components for the apparatus.
transducer must satisfy the deflection requirement of 6.9. The
6.2 Vertical Loading Device—Asuitabledeviceforapplying
slide table shall allow a sufficient displacement to provide a
vertical force to the specimen that must be capable of main-
minimum of 30 % shear strain.
taining constant force during the consolidation phase of a test,
permit quick application of force for consolidation increments, 6.7 Lateral Confinement Device—The specimen shall be
constrained laterally such that the cross-sectional area at any
and allow continuous adjustment of force when using active
height control or be rigidly locked in place when using passive location does not change by more than 0.1 % during shear. In
addition, the confinement must allow uniform shear deforma-
height control.
tion. Circular specimens are generally confined by a wire
6.3 Shear Loading Device—A suitable device for applying
reinforced membrane or stacked rigid rings. Square specimens
shear force to the specimen with sufficient capacity and control
generally are confined by stacked hollow plates or hinged solid
to deform the specimen at the required displacement rate.
plates. The thickness of the individual stacked rings or plates
Displacement should be smooth and continuous. At a
must be less than ⁄10 of the specimen thickness in order to
minimum, the displacement rate should be within 615 % of
allow relatively uniform shear deformation. When the confin-
the average calculated rate (12.3.7) from 50 % of the peak
ing device is within a water bath, it shall be constructed of
shear force to the end of the test. Vibration due to operation of
corrosion resistant material.
this device should be sufficiently small so as not to cause
6.7.1 Specimen Size Requirements:
visible ripples in a glass of water placed on the loading
6.7.1.1 The minimum specimen diameter (or lateral dimen-
platform.
sion) shall be 45 mm.
6.4 Force Transducer—Two suitable transducers: one for
6.7.1.2 The minimum specimen height shall be 12 mm.
measuring vertical force and one for measuring shear force.
6.7.1.3 The height to diameter, or minimum lateral
Each transducer shall have the necessary capacity, be accurate
dimension, ratio shall not exceed 0.4.
to 61 % of the applied maximum force for a given test and
6.7.1.4 The specimen height shall not be less than ten times
have a readability of at least 4 significant digits of the applied
the maximum particle diameter (see 9.4).
maximum force for a given test. The transducers shall be
insensitive to eccentric loading or installed in a fashion to 6.7.2 Platens—The top and bottom platens of the apparatus
eliminate eccentric loading. The compressibility of the shear shall be constructed of corrosion resistant material and have a
measuring transducer shall not cause the deviation in shear circular, rectangular or square cross-section to match the
displacement rate to exceed6 15 % of the average rate. When specimen. The platens shall be designed to securely hold the
FIG. 1 Schematic Diagram of Direct Simple Shear Components
D6528 − 17
porous disks and provide drainage from the specimen to the frame must allow the trimmed specimen to be transferred from
water bath and transfer shear to the specimen without horizon- thetrimmingdevicetotheconfinementdevicewithaminimum
of disturbance.
tal slippage.
6.7.3 Porous Disks—Theporousdisksshallbebrass,silicon
6.12 Water Access System—A method to provide the speci-
carbide, aluminum oxide, or similar rigid corrosion resistant
men with free access to water at atmospheric pressure and
material. The disks shall be flat, fine enough to prevent
prevent specimen drying due to evaporation. The entire speci-
intrusion of the soil into the pores, and rough enough to
menandconfinementdevicemaybesubmergedinawaterbath
transfer the shear stress. The disks must be at least ten times
or the end platens may be connected to a standpipe by flexible
more permeable than the soil. Disks must cover at least 90 % tubing. In either case, water must be available to both ends of
of the specimen surface and when smaller than the specimen,
the specimen by means of the porous disks.
mustberecessedintotheplatensuchthatthesurfaceincontact
6.13 Miscellaneous Equipment—Including timing device
with the soil is flush with the platen.
with one second readability, caliper, distilled or demineralized
water, spatulas, knives, trimming blade and wire saws.
NOTE 2—It is sometimes necessary to increase the surface roughness of
the porous disks in order to prevent interface slippage. Short metallic pins
6.14 Balances, in accordance with Test Methods D2216.
cemented into the disks, knife edges and ridges have been used success-
fully but may introduce uncertainty in test results. 6.15 Drying Oven,inaccordancewithTestMethodsD2216.
6.16 Water Content Container, in accordance with Test
6.8 Displacement Indicators—Two suitable devices: one to
Methods D2216.
measure the change in specimen height and one for measuring
the shear deformation (vertical and lateral movement of top
6.17 Environment—Tests shall be performed in an environ-
platen relative to bottom platen). These devices shall have a
mentwheretemperaturefluctuationsarelessthan 62°Cduring
range of at least 50 % of the initial height of the specimen and
shear, and there is no direct exposure to sunlight.
shall have an accuracy of 0.25 %, or better of full range and a
6.18 Trimming Environment—Trim the specimen in a glove
readability of at least 4 significant digits of the initial specimen
box or room that has a high enough relative humidity to
height.
prevent changes in the water content of the soil.
6.9 Volume Control Equipment—One of the two following
6.19 Specimen Height Measurement Devices—A dial com-
methods may be used to achieve constant volume during shear.
parator or another suitable device shall be used to measure the
With either method, the specimen is free to drain and the
height to four significant digits and shall be constructed so that
measured change in vertical stress during shear is assumed to
its use will not indent or penetrate into the specimen.
be equal to the pore pressure which would develop in a sealed
specimen confined by a constant vertical total stress. In either
7. Sampling
case, the device shall not allow the specimen change in height
7.1 Intact Samples:
to exceed 0.05 % including the equipment deformation deter-
7.1.1 Intact samples having satisfactory quality for testing
mined in 10.1.
by this method may be obtained using procedures and appara-
6.9.1 Vertical Force Adjustment Device—Active height con-
tus described by Practices D1587 and D3550. Specimens also
trol requires a mechanism to continuously adjust the vertical
may be trimmed from large intact block samples obtained and
force to prevent changes in the specimen height during shear.
sealed in the field.
7.1.2 Intact samples to be tested by this method shall be
NOTE 3—Avariety of devices are used including manual adjustment of
a worm gear, computer control of a worm gear, and computer control of preserved, handled and transported in accordance with the
a pneumatic cylinder.
practices for Groups C and D samples in Practice D4220.
7.1.3 Intact samples shall be sealed and stored such that no
6.9.2 Vertical Displacement Clamp—Passive height control
moisture is lost or gained between sampling and testing.
requires a mechanism to lock the vertical loading ram in place
Storage time and temperature fluctuations should be reduced.
during shear. The vertical force transducer must be moment
7.1.4 The quality of simple shear test results diminish
insensitive and located between the specimen and the clamp or
greatly with sample disturbance. No sampling procedure can
the specimen and the slide base.
produce completely undisturbed samples; therefore, careful
6.10 Specimen Trimming Device (Optional)—A trimming
evaluation of the sample and selection of the highest quality
turntable or a cylindrical cutting ring may be used for cutting
material for testing is recommended for reliable testing.
the cylindrical specimens to the proper diameter. A wire saw
NOTE 4—Evaluation for sample disturbance, stones or other inclusions,
and miter box or cutting shoe may be used for rectangular
and selection of specimen location is greatly facilitated by x-ray radiog-
specimens. The top and bottom of the specimen may be rough
raphy of the samples as described in Methods D4452.
trimmed with a wire saw. The flat surfaces must be finish
7.2 Laboratory Reconstituted and Compacted Specimens:
trimmed with a sharpened straight edge and shall have a
7.2.1 Laboratory reconstituted and compacted specimens
tolerance of 60.05 mm.
may be prepared from bulk homogeneous material.
6.11 Specimen Setup Frame—A rigid frame to hold in 7.2.2 Bulk material should be handled and transported in
alignment the bottom platen, the specimen in the trimming accordancewiththepracticesforGroupBsamplesofPractices
device, and expander containing the confinement device. The D4220.
D6528 − 17
7.2.2.1 The material required for the specimen shall be 8.4.3 When soil is compacted into an oversize preparation
batched by thoroughly mixing soil with sufficient water to mold, compact using more than three layers and then trim the
produce the desired conditions. After batching, store the specimen using the intact preparation procedures.
material in a covered container for at least 16 hours prior to
8.5 Trim the top and bottom surfaces of the specimen to be
specimen preparation.
flat and perpendicular to the specimen sides. This trimming
may be accomplished using the rims of the cutting shoe or an
8. Specimen Preparation
additional alignment device. For soft to medium soils, a wire
8.1 Reasonable precautions should be taken to reduce the
saw should be used to rough cut the surface. For stiff soils, and
potential for disturbance of the soil caused by vibration,
the final surfaces, a straightedge with a sharpened cutting
distortion, and compression.
surface should be used to make sure the surfaces are flat.
8.2 Test specimens and soil processing should be performed
8.6 If a small rock particle is encountered in the surfaces
in an environment that prevents moisture change.
being trimmed, it should be removed and the resulting void
8.3 Intact Specimens—Trim the sample to the lateral dimen-
filled with soil from the trimmings.
sion of the lateral confinement device to obtain the specimen.
8.3.1 Intact soil collected using sample tubes shall be at
8.7 Obtain two or three initial water content determinations
least 2.5 mm larger in each dimension than the specimen of the soil in accordance with Test Methods D2216 from
dimensionexceptasspecifiedin8.3.2and8.3.3.Trimawaythe
material trimmed adjacent to the test specimen if sufficient
additional material using one of the following methods. material is available or from the excess batched material.
NOTE 5—The degree of sample disturbance is known to increase
8.8 Determine the initial moist mass of the specimen (M )
to
towards the perimeter of the tube sample, and therefore, it is better to use
to the nearest 0.01 g by direct measurement or when in the
larger diameter samples where possible.
cutting shoe by measuring the mass of the shoe with specimen
8.3.1.1 When using a trimming turntable and cylindrical
and subtracting the tare mass of the shoe.
specimens, make a complete perimeter cut, the width of the
8.9 Determine the initial height ( H ) of the specimen to the
blade, to reduce the soil diameter to that of the confinement o
nearest 0.025 mm by taking the average of at least four evenly
ring. Gradually advance the specimen into the ring by the
spaced measurements using a dial comparator or other suitable
width of the blade. Repeat until the specimen protrudes from
measuring device.
the bottom of the ring.
8.3.1.2 When using a cutting shoe, trim the soil to a gentle
8.10 Use the specimen setup frame to insert the fully
taper in front of the cutting surface with a knife or spatula.
trimmed specimen into the confinement device.
Afterthetaperisformed,ad
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