ASTM D7181-20
(Test Method)Standard Test Method for Consolidated Drained Triaxial Compression Test for Soils
Standard Test Method for Consolidated Drained Triaxial Compression Test for Soils
SIGNIFICANCE AND USE
5.1 The shear strength of a saturated soil in triaxial compression depends on the stresses applied, time of consolidation, strain rate, and the stress history experienced by the soil.
5.2 In this test method, the shear characteristics are measured under drained conditions and are applicable to field conditions where soils have been fully consolidated under the existing normal stresses and the normal stress changes under drained conditions similar to those in the test method.
5.3 The shear strength determined from this test method can be expressed in terms of effective stress because a strain rate or load application rate slow enough to allow pore pressure dissipation during shear is used to result in negligible excess pore pressure conditions. The shear strength may be applied to field conditions where full drainage can occur (drained conditions), and the field stress conditions are similar to those in the test method.
5.4 The shear strength determined from the test can be used in embankment stability analyses, earth pressure calculations, and foundation design.
Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers the determination of strength and stress-strain relationships of a cylindrical specimen of either intact or reconstituted soil. Specimens are consolidated and sheared in compression with drainage at a constant rate of axial deformation (strain controlled).
1.2 This test method provides for the calculation of principal stresses and axial compression by measurement of axial load, axial deformation, and volumetric changes.
1.3 This test method provides data useful in determining strength and deformation properties such as Mohr strength envelopes. Generally, three specimens are tested at different effective consolidation stresses to define a strength envelope. The stresses should be specified by the engineer requesting the test. A test on a new specimen is required for each consolidation stress.
1.4 If this test method is used on cohesive soil, a test may take weeks to complete.
1.5 The determination of strength envelopes and the development of relationships to aid in interpreting and evaluating test results are beyond the scope of this test method and must be performed by a qualified, experienced professional.
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.
1.6.1 The procedures used to specify how data are collected, calculated, or recorded in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variations, purpose for obtaining the data, special purpose studies or any consideration for the user’s objectives; and it is common practice to increase or reduce the significant digits of the reported data to be commensurate with these considerations. It is beyond the scope of this test standard to consider significant digits used in analysis methods for engineering design.
1.7 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are mathematical conversions, which are provided for information purposes only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as non-conformance with this test method.
1.7.1 The g...
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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: D7181 − 20
Standard Test Method for
1
Consolidated Drained Triaxial Compression Test for Soils
This standard is issued under the fixed designation D7181; 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 of this test standard to consider significant digits used in
analysis methods for engineering design.
1.1 This test method covers the determination of strength
and stress-strain relationships of a cylindrical specimen of 1.7 Units—The values stated in SI units are to be regarded
either intact or reconstituted soil. Specimens are consolidated as standard. The inch-pound units given in parentheses are
and sheared in compression with drainage at a constant rate of mathematical conversions, which are provided for information
axial deformation (strain controlled). purposes only and are not considered standard. Reporting of
test results in units other than SI shall not be regarded as
1.2 This test method provides for the calculation of princi-
non-conformance with this test method.
pal stresses and axial compression by measurement of axial
1.7.1 The gravitational system of inch-pound units is used
load, axial deformation, and volumetric changes.
when dealing with inch-pound units. In this system, the pound
1.3 This test method provides data useful in determining
(lbf)representsaunitofforce(weight),whiletheunitformass
strength and deformation properties such as Mohr strength
is slugs. The slug unit is not given, unless dynamic (F = ma)
envelopes. Generally, three specimens are tested at different
calculations are involved.
effective consolidation stresses to define a strength envelope.
1.7.2 It is common practice in the engineering/construction
The stresses should be specified by the engineer requesting the
profession to concurrently use pounds to represent both a unit
test. A test on a new specimen is required for each consolida-
of mass (lbm) and of force (lbf). This implicitly combines two
tion stress.
separate systems of units: that is, the absolute system and the
gravitational system. It is scientifically undesirable to combine
1.4 If this test method is used on cohesive soil, a test may
take weeks to complete. theuseoftwoseparatesetsofinch-poundunitswithinasingle
standard. As stated, this standard includes the gravitational
1.5 The determination of strength envelopes and the devel-
system of inch-pound units and does not use/present the slug
opment of relationships to aid in interpreting and evaluating
unitformass.However,theuseofbalancesorscalesrecording
test results are beyond the scope of this test method and must
3
pounds of mass (lbm) or recording density in lbm/ft shall not
be performed by a qualified, experienced professional.
be regarded as non-conformance with this standard.
1.6 All observed and calculated values shall conform to the
1.7.3 The terms density and unit weight are often used
guidelines for significant digits and rounding established in
interchangeably. Density is mass per unit volume whereas unit
Practice D6026.
weight is force per unit volume. In this standard density is
1.6.1 Theproceduresusedtospecifyhowdataarecollected,
given only in SI units. After the density has been determined,
calculated, or recorded in this standard are regarded as the
the unit weight is calculated in SI or inch-pound units, or both.
industry standard. In addition, they are representative of the
1.8 This standard may involve hazardous materials,
significant digits that generally should be retained. The proce-
operations, and equipment. This standard does not purport to
dures used do not consider material variations, purpose for
address all of the safety concerns, if any, associated with its
obtainingthedata,specialpurposestudiesoranyconsideration
use. It is the responsibility of the user of this standard to
for the user’s objectives; and it is common practice to increase
establish appropriate safety, health, and environmental prac-
or reduce the significant digits of the reported data to be
tices and determine the applicability of regulatory limitations
commensuratewiththeseconsiderations.Itisbeyondthescope
prior to use.
1.9 This international standard was developed in accor-
1
dance with internationally recognized principles on standard-
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
ization established in the Decision on Principles for the
Comp
...
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: D7181 − 11 D7181 − 20
Standard Test Method for
1
Consolidated Drained Triaxial Compression Test for Soils
This standard is issued under the fixed designation D7181; 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 covers the determination of strength and stress-strain relationships of a cylindrical specimen of either intact
or reconstituted soil. Specimens are consolidated and sheared in compression with drainage at a constant rate of axial deformation
(strain controlled).
1.2 This test method provides for the calculation of principal stresses and axial compression by measurement of axial load, axial
deformation, and volumetric changes.
1.3 This test method provides data useful in determining strength and deformation properties such as Mohr strength envelopes.
Generally, three specimens are tested at different effective consolidation stresses to define a strength envelope. The stresses should
be specified by the engineer requesting the test. A test on a new specimen is required for each consolidation stress.
1.4 If this test method is used on cohesive soil, a test may take weeks to complete.
1.5 The determination of strength envelopes and the development of relationships to aid in interpreting and evaluating test
results are beyond the scope of this test method and must be performed by a qualified, experienced professional.
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.6.1 The methodsprocedures used to specify how data are collected, calculated, or recorded in this standard are regarded as
the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures
used do not consider material variations, purpose for obtaining the data, special purpose studies or any consideration of the end
use. for the user’s objectives; and it is common practice to increase or reduce the significant digits of the reported data to be
commensurate with these considerations. It is beyond the scope of this test methodstandard to consider significant digits used in
analysis methods for engineering design.
1.7 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are
mathematical conversions, which are provided for information purposes only and are not considered standard. Reporting of test
results in units other than SI shall not be regarded as non-conformance with this test method.
1.7.1 The gravitational system of inch-pound units is used when dealing with inch-pound units. In this system, the pound (lbf)
represents a unit of force (weight), while the unit for mass is slugs. The slug unit is not given, unless dynamic (F = ma) calculations
are involved.
1.7.2 It is common practice in the engineering/construction profession to concurrently use pounds to represent both a unit of
mass (lbm) and of force (lbf). This implicitly combines two separate systems of units: that is, the absolute system and the
gravitational system. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single
standard. As stated, this standard includes the gravitational system of inch-pound units and does not use/present the slug unit for
3
mass. However, the use of balances or scales recording pounds of mass (lbm) or recording density in lbm/ft shall not be regarded
as non-conformance with this standard.
1.7.3 The terms density and unit weight are often used interchangeably. Density is mass per unit volume whereas unit weight
is force per unit volume. In this standard density is given only in SI units. After the density has been determined, the unit weight
is calculated in SI or inch-pound units, or both.
1.8 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all
of the safety concerns, if any, 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.
1
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommi
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