ASTM D7608-18
(Test Method)Standard Test Method for Torsional Ring Shear Test to Measure Drained Fully Softened Shear Strength and Stress Dependent Strength Envelope of Fine-Grained Soils
Standard Test Method for Torsional Ring Shear Test to Measure Drained Fully Softened Shear Strength and Stress Dependent Strength Envelope of Fine-Grained Soils
SIGNIFICANCE AND USE
5.1 The ring shear apparatus maintains the cross-sectional area of the shear surface constant during shear and shears the specimen continuously in one rotational direction for any magnitude of shear displacement and along the entire specimen cross-sectional area.
5.2 The ring shear apparatus allows a reconstituted specimen to be consolidated at the desired normal stress prior to drained shearing. This simulates the field conditions under which complete softening develops in overconsolidated clays, claystones, mudstones, and shales that do not have a pre-existing shear surface, sheared bedding planes, joints, or faults as described by Skempton (19702 and 19773) and unfailed compacted fill slopes (Gamez and Stark 20144) because the fully softened strength corresponds to the peak shear strength of a normally consolidated fine-grained soil. The fully softened strength is only applicable to the soil zones that are subject to the environmental deterioration and applied shear stresses that lead to soil softening, deterioration of soil fabric, and strength loss, which may not be relevant to all slopes and all depths. The fully softened strength should be used in an effective stress/drained stability analysis using a stress dependent strength envelope for slopes with no prior shearing.
5.3 The ring shear test is suited to the determination of the drained fully softened shear strength because of the short drainage path through the thin specimen, small post-peak strength loss in a normally consolidated specimen, and the constant cross-sectional area.
5.4 The ring shear test specimen is annular so the angular displacement differs from the inner radius to the outer radius. This is not significant because a normally consolidated specimen does not exhibit a large post-peak strength loss so the difference in peak shear resistance at the inner radius and outer radius at different displacements is not significant and the ratio of the inner to outer radii of the ring is great...
SCOPE
1.1 This test method provides a procedure for performing a torsional ring shear test under a drained condition to measure the fully softened shear strength and stress dependent strength envelope of fine-grained soils (using a reconstituted normally consolidated specimen). The fully softened strength and the corresponding stress dependent effective stress strength envelope are used to evaluate the stability of slopes that do not have a pre-existing shear surface but have been subjected to environmental conditions and shear stresses that lead to soil softening, deterioration of the soil fabric, and strength loss. It has been shown (Skempton 19702 and 19773) that under these conditions and within the depth zones that have undergone softening, first-time slope failures can occur at effective stress levels that correspond to a fully softened strength envelope. It has also been shown empirically (Skempton 19702 and 19773) that fully softened strength of fine grained soils can be approximated by the peak strength of a reconstituted and normally consolidated specimen. In this test method, reconstituted and normally consolidated specimens are sheared at a controlled and constant displacement rate until the peak shear resistance has been obtained. Generally, the drained fully softened failure envelope is determined at three or more effective normal stresses. A separate test specimen must be used for each normal stress to measure the fully softened strength otherwise a post-peak or even drained residual strength will be measured if the same specimen is used at the same or at another effective normal stress because of the existence of a prior shear surface.
1.2 The ring shear apparatus allows a reconstituted specimen to be normally consolidated at the desired normal stress prior to drained shearing. The test results closely simulate the fully softened strength of stiff natural fine-grained soils (Skempton 19702 and 19773) and com...
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Designation: D7608 − 18
Standard Test Method for
Torsional Ring Shear Test to Measure Drained Fully
Softened Shear Strength and Stress Dependent Strength
1
Envelope of Fine-Grained Soils
This standard is issued under the fixed designation D7608; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope prior to drained shearing. The test results closely simulate the
fully softened strength of stiff natural fine-grained soils
1.1 This test method provides a procedure for performing a
2 3
(Skempton 1970 and 1977 ) and compacted fills of fine-
torsional ring shear test under a drained condition to measure
4
grained soils (Gamez and Stark 2014 ). This simulates the
the fully softened shear strength and stress dependent strength
mobilized shear strength in overconsolidated clays, claystones,
envelope of fine-grained soils (using a reconstituted normally
mudstones, and shales in natural slopes and compacted fill in
consolidated specimen). The fully softened strength and the
manmade slopes, such as, dams, levees, and highway
corresponding stress dependent effective stress strength enve-
embankments, after the soil has fully softened and attained the
lopeareusedtoevaluatethestabilityofslopesthatdonothave
fully softened strength condition.
a pre-existing shear surface but have been subjected to envi-
ronmental conditions and shear stresses that lead to soil 1.3 A shear stress-displacement relationship may be ob-
softening, deterioration of the soil fabric, and strength loss. It tained from this test method. However, a shear stress-strain
2 3
has been shown (Skempton 1970 and 1977 ) that under these relationship or any associated quantity, such as modulus,
conditions and within the depth zones that have undergone cannot be determined from this test method because defining
softening, first-time slope failures can occur at effective stress the height of the shear zone is difficult and needed in the shear
levels that correspond to a fully softened strength envelope. It strain calculations.As a result, the height of this shear zone is
2 3
has also been shown empirically (Skempton 1970 and 1977 ) unknown, so an accurate or representative shear strain can
that fully softened strength of fine grained soils can be therefore not be determined.
approximated by the peak strength of a reconstituted and
1.4 The selection of normal stresses and final determination
normally consolidated specimen. In this test method, reconsti-
of the shear strength envelope for design analyses and the
tuted and normally consolidated specimens are sheared at a
criteria to interpret and evaluate the test results are the
controlled and constant displacement rate until the peak shear
responsibility of the engineer or entity requesting the test.
resistance has been obtained. Generally, the drained fully
1.5 Units—The values stated in SI units are to be regarded
softened failure envelope is determined at three or more
asthestandard.Thevaluesgiveninparenthesesaremathemati-
effective normal stresses. A separate test specimen must be
cal conversions to inch-pound units that are provided for
used for each normal stress to measure the fully softened
information only and are not considered standard.
strength otherwise a post-peak or even drained residual
strength will be measured if the same specimen is used at the 1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
same or at another effective normal stress because of the
existence of a prior shear surface. responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.2 The ring shear apparatus allows a reconstituted speci-
mine the applicability of regulatory limitations prior to use.
men to be normally consolidated at the desired normal stress
1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
ization established in the Decision on Principles for the
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
Compressibility of Soils.
Development of International Standards, Guides and Recom-
CurrenteditionapprovedJune1,2018.PublishedJuly2018.Originallyapproved
mendations issued by the World Trade Organization Technical
in 2010. Last previous edition approved in 2010 as D7263–10. DOI: 10.1520/
Barriers to Trade (TBT) Committee.
D7608–18.
2
Skempton, A. (1970). “First-time slides in over-consolidated clays.”
Géotechnique, 20(3), 320–324.
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7608 − 10 D7608 − 18
Standard Test Method for
Torsional Ring Shear Test to DetermineMeasure Drained
Fully Softened Shear Strength and Nonlinear Stress
Dependent Strength Envelope of Cohesive Soils (Using
Normally Consolidated Specimen) for Slopes with No
1
Preexisting Shear SurfacesFine-Grained Soils
This standard is issued under the fixed designation D7608; 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
1.1 This test method provides a procedure for performing a torsional ring shear test under a drained condition to
determinemeasure the fully softened shear strength and nonlinear stress dependent strength envelope of cohesive soils. fine-grained
soils (using a reconstituted normally consolidated specimen). The fully softened strength is and the corresponding stress dependent
effective stress strength envelope are used to evaluate the stability of slopes that do not have a preexisting shear surface. In addition,
the pre-existing shear surface but have been subjected to environmental conditions and shear stresses that lead to soil softening,
2 3
deterioration of the soil fabric, and strength loss. It has been shown (Skempton 1970 and 1977 fully softened shear strength
corresponds to ) that under these conditions and within the depth zones that have undergone softening, first-time slope failures can
occur at effective stress levels that correspond to a fully softened strength envelope. It has also been shown empirically (Skempton
2 3
1970 and 1977 the peak shear ) that fully softened strength of fine grained soils can be approximated by the peak strength of a
reconstituted and normally consolidated specimen. This test method focuses on the use of a reconstituted specimen to measure the
fully softened strength. This test method is performed by shearing a normally consolidated, reconstituted specimen In this test
method, reconstituted and normally consolidated specimens are sheared at a controlled and constant displacement rate until the
peak shear resistance has been obtained. Generally, the drained fully softened failure envelope is determined at three or more
effective normal stresses. A separate test specimen must be used for each normal stress to measure the fully softened strength
otherwise a post-peak or even drained residual strength will be measured if the same specimen is used at the same or at another
effective normal stress because of the existence of a prior shear surface.
1.2 The ring shear apparatus allows a reconstituted specimen to be normally consolidated at the desired normal stress prior to
2
drained shearing. The test results closely simulate the fully softened strength of stiff natural fine-grained soils (Skempton 1970
3 4
and 1977 ) and compacted fills of fine-grained soils (Gamez and Stark 2014 ). This simulates the field conditions under which the
fully softened strength develops mobilized shear strength in overconsolidated clays, claystones, mudstones, and shales.shales in
natural slopes and compacted fill in manmade slopes, such as, dams, levees, and highway embankments, after the soil has fully
softened and attained the fully softened strength condition.
1.3 A shear stress-displacement relationship may be obtained from this test method. However, a shear stress-strain relationship
or any associated quantity, such as modulus, cannot be determined from this test method because possible soil extrusion and
volume change prevents defining the heightdefining the height of the shear zone is difficult and needed in the shear strain
calculations. As a result, shear strain cannot be calculated but shear displacement can be calculated.the height of this shear zone
is unknown, so an accurate or representative shear strain can therefore not be determined.
1.4 The selection of normal stresses and final determination of the shear strength envelope for design analyses and the criteria
to interpret and evaluate the test results are the responsibility of the engineer or officeentity requesting the test.
1
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
Compressibility of Soils.
Current edition approved May 15, 2010June 1, 2018. Published July 2010July 2018. Originally approved in 2010. Last previous edit
...
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