Method for Consolidated Drained Triaxial Compression Test for Soils

SIGNIFICANCE AND USE
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.
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.
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 minimize 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.
The shear strength determined from the test is commonly used in embankment stability analyses, earth pressure calculations, and foundation design.
Note 1—Notwithstanding the statements on precision and bias contained in this test method, the precision of this test method 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 testing. Users of this test method are cautioned that compliance with Practice D3740 does not ensure reliable testing. Reliable testing depends on several 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.
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 methods 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. It is beyond the scope of this test method 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 prac...

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ASTM D7181-11 - Method for Consolidated Drained Triaxial Compression Test for Soils
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7181 − 11
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 test results in units other than SI shall not be regarded as
non-conformance with this test method.
1.1 This test method covers the determination of strength
1.7.1 The gravitational system of inch-pound units is used
and stress-strain relationships of a cylindrical specimen of
when dealing with inch-pound units. In this system, the pound
either intact or reconstituted soil. Specimens are consolidated
(lbf)representsaunitofforce(weight),whiletheunitformass
and sheared in compression with drainage at a constant rate of
is slugs. The slug unit is not given, unless dynamic (F = ma)
axial deformation (strain controlled).
calculations are involved.
1.2 This test method provides for the calculation of princi-
1.7.2 It is common practice in the engineering/construction
pal stresses and axial compression by measurement of axial
profession to concurrently use pounds to represent both a unit
load, axial deformation, and volumetric changes.
of mass (lbm) and of force (lbf). This implicitly combines two
separate systems of units: that is, the absolute system and the
1.3 This test method provides data useful in determining
gravitational system. It is scientifically undesirable to combine
strength and deformation properties such as Mohr strength
theuseoftwoseparatesetsofinch-poundunitswithinasingle
envelopes. Generally, three specimens are tested at different
standard. As stated, this standard includes the gravitational
effective consolidation stresses to define a strength envelope.
system of inch-pound units and does not use/present the slug
1.4 If this test method is used on cohesive soil, a test may
unitformass.However,theuseofbalancesorscalesrecording
take weeks to complete. 3
pounds of mass (lbm) or recording density in lbm/ft shall not
1.5 The determination of strength envelopes and the devel- be regarded as non-conformance with this standard.
opment of relationships to aid in interpreting and evaluating
1.7.3 The terms density and unit weight are often used
test results are beyond the scope of this test method and must interchangeably. Density is mass per unit volume whereas unit
be performed by a qualified, experienced professional.
weight is force per unit volume. In this standard density is
given only in SI units. After the density has been determined,
1.6 All observed and calculated values shall conform to the
the unit weight is calculated in SI or inch-pound units, or both.
guidelines for significant digits and rounding established in
Practice D6026. 1.8 This standard may involve hazardous materials,
operations, and equipment. This standard does not purport to
1.6.1 The methods used to specify how data are collected,
address all of the safety concerns, if any, associated with its
calculated, or recorded in this standard are regarded as the
use. It is the responsibility of the user of this standard to
industry standard. In addition, they are representative of the
establish appropriate safety and health practices and deter-
significant digits that generally should be retained. The proce-
mine the applicability of regulatory limitations prior to use.
dures used do not consider material variations, purpose for
obtainingthedata,specialpurposestudiesoranyconsideration
2. Referenced Documents
of the end use. It is beyond the scope of this test method to
2
consider significant digits used in analysis methods for engi-
2.1 ASTM Standards:
neering design. D422Test Method for Particle-Size Analysis of Soils
D653Terminology Relating to Soil, Rock, and Contained
1.7 Units—The values stated in SI units are to be regarded
Fluids
as standard. The inch-pound units given in parentheses are
D854Test Methods for Specific Gravity of Soil Solids by
mathematical conversions, which are provided for information
Water Pycnometer
purposes only and are not considered standard. Reporting of
D1587Practice for Thin-Walled Tube Sampling of Soils for
Geotechnical Purposes
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
2
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Compressibility of Soils. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved July 1, 2011. Published August 2011. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Sum
...

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