ASTM D7012-07
(Test Method)Standard Test Method for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures
Standard Test Method for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures
SIGNIFICANCE AND USE
The parameters obtained from these procedures are in terms of undrained total stress (as already mentioned in 1.1.1.). However, there are some cases where either the rock type or the loading condition of the problem under consideration will require the effective stress or drained parameters be determined.
Unconfined compressive strength of rock is used in many design formulas and is sometimes used as an index property to select the appropriate excavation technique. Deformation and strength of rock are known to be functions of confining pressure. The confined compression test is commonly used to simulate the stress conditions under which most underground rock masses exist. The elastic constants are used to calculate the stress and deformation in rock structures.
The deformation and strength properties of rock cores measured in the laboratory usually do not accurately reflect large-scale in situ properties because the latter are strongly influenced by joints, faults, inhomogeneities, weakness planes, and other factors. Therefore, laboratory values for intact specimens must be employed with proper judgment in engineering applications.
Note 2—Notwithstanding the statements on precision and bias contained in this test method; the measures of precision of these test methods are dependent on the competence of the personnel performing them, and on the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D 3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D 3740 provides a means for evaluating some of those factors.
SCOPE
1.1 This test method covers the determination of the strength of intact rock core specimens in uniaxial compression and confined compression. The tests provide data in determining the strength of rock, namely: the uniaxial strength, shear strengths at varying pressures and varying temperatures, angle of internal friction, (angle of shearing resistance), and cohesion intercept. The test method specifies the apparatus, instrumentation, and procedures for determining the stress-axial strain and the stress-lateral strain curves, as well as Young's modulus, E, and Poisson's ratio, . It should be observed that this method makes no provision for pore pressure measurements and specimens are undrained (platens are not vented). Thus the strength values determined are in terms of total stress, that is, are not corrected for pore pressures. This test method does not include the procedures necessary to obtain a stress-strain curve beyond the ultimate strength.
1.1.1 This standard replaces and combines the following Standard Test Methods for: D 2664 Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements; D 5407 Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure Measurements; D 2938 Unconfined Compressive Strength of Intact Rock Core Specimens; and D 3148 Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression.
1.1.2 The original four standards are now referred to as Methods in this standard as follows: Method A - Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements; Method B - Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure Measurements; Method C - Unconfined Compressive Strength of Intact Rock Core Specimens; Method D - Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression; and Option A - Elevated Temperatures.
1.2 For an isotropic material, the relation between the shear and bulk moduli and Young's modulus and Poisson's ratio are:Equation 1 - G = E/21 + Equation 2 - K = E/31 2where:Gshear modulus,Kbulk modulus, EYoung's modulus, and Poisson's ratio.
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General Information
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Standards Content (Sample)
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Designation: D 7012 – 07
Standard Test Method for
Compressive Strength and Elastic Moduli of Intact Rock
Core Specimens under Varying States of Stress and
1
Temperatures
This standard is issued under the fixed designation D 7012; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope mens; Method D — Elastic Moduli of Intact Rock Core
SpecimensinUniaxialCompression;andOptionA—Elevated
1.1 This test method covers the determination of the
Temperatures.
strength of intact rock core specimens in uniaxial compression
1.2 For an isotropic material, the relation between the shear
and confined compression. The tests provide data in determin-
and bulk moduli andYoung’s modulus and Poisson’s ratio are:
ing the strength of rock, namely: the uniaxial strength, shear
strengths at varying pressures and varying temperatures, angle E
G 5 (1)
2 11y!
ofinternalfriction,(angleofshearingresistance),andcohesion ~
intercept. The test method specifies the apparatus, instrumen-
E
K 5 (2)
tation, and procedures for determining the stress-axial strain
3 1 2 2y
~ !
andthestress-lateralstraincurves,aswellasYoung’smodulus,
where:
E,andPoisson’sratio, y.Itshouldbeobservedthatthismethod
G = shear modulus,
makes no provision for pore pressure measurements and
K = bulk modulus,
specimens are undrained (platens are not vented). Thus the
E = Young’s modulus, and
strength values determined are in terms of total stress, that is,
y = Poisson’s ratio.
are not corrected for pore pressures. This test method does not
1.2.1 The engineering applicability of these equations de-
include the procedures necessary to obtain a stress-strain curve
creases with increasing anisotropy of the rock. It is desirable to
beyond the ultimate strength.
conduct tests in the plane of foliation, cleavage or bedding and
1.1.1 This standard replaces and combines the following
at right angles to it to determine the degree of anisotropy. It is
Standard Test Methods for: D 2664 Triaxial Compressive
notedthatequationsdevelopedforisotropicmaterialsmaygive
Strength of Undrained Rock Core Specimens Without Pore
only approximate calculated results if the difference in elastic
Pressure Measurements; D 5407 Elastic Moduli of Undrained
moduli in two orthogonal directions is greater than 10 % for a
Rock Core Specimens in Triaxial Compression Without Pore
given stress level.
Pressure Measurements; D 2938 Unconfined Compressive
Strength of Intact Rock Core Specimens; and D 3148 Elastic NOTE 1—Elastic moduli measured by sonic methods (Test Method
D 2845) may often be employed as preliminary measures of anisotropy.
Moduli of Intact Rock Core Specimens in Uniaxial Compres-
sion.
1.3 This test method given for determining the elastic
1.1.2 The original four standards are now referred to as
constants does not apply to rocks that undergo significant
Methods in this standard as follows: Method A — Triaxial
inelastic strains during the test, such as potash and salt. The
Compressive Strength of Undrained Rock Core Specimens
elastic moduli for such rocks should be determined from
Without Pore Pressure Measurements; Method B — Elastic
unload-reload cycles, that are not covered by this test method.
Moduli of Undrained Rock Core Specimens in Triaxial Com-
1.4 The values stated in SI units are to be regarded as the
pression Without Pore Pressure Measurements; Method C —
standard.
Unconfined Compressive Strength of Intact Rock Core Speci-
1.5 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 appro-
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
priate safety and health practices and determine the applica-
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved July 1, 2007. Published July 2007. Originally approved
bility of regulatory limitations prior to use.
e1
in 2004. Last previous edition approved in 2004 as D 7012–04 .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D7012–07
NOTE 2—Notwithstanding the statements on precision and bias con-
2. Referenced Documents
tained in this test method; the measures of precision of these test methods
2
2.1 ASTM Standards:
are dependent on the competence of the personnel performing them, and
D 2216 Test Methods for Laboratory Determination of Wa-
on the suitability of the equipment and facilities used.Agencies that meet
ter (Moisture) Content
...
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