ASTM D7012-04
(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
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.
1.1.3 The original four standards are now referred to as Methods in this standard as follows: Method A (D2664) Triaxial Compressive Strength of Undarined Rock Core Specimens Without Pore Pressure Measurements; Method B (D5407) Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure Measurements, Method C (D2938 Unconfined Compressive Strength of Intact Rock Core Specimens; Method D (d3148) Elastic Moduli of Intact Rock Core Specimerns 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.
1.2.1 The engineering applicability of these equations decreases with increasing anisotropy of the rock. It is desirable to conduct tests in the plane of foliation, cleavage or bedding and at right angles to it to determine the degree of anisotropy. It is noted that equations developed for isotropic materials may give only approximate calculated results if the difference in elastic moduli in two orthogonal directions is greater than 10 % for a given stress level.Note 1
Elastic moduli measured by sonic methods (Test Method D 2845) may often be employed as preliminary measures of anisotropy.
1.3 This test method given for determining the elastic constants does not apply to rocks that undergo significant inelastic strains during the test, such as potash and salt. The elastic moduli for such rocks should be determined from unload-reload cycles, that are not covered by this test method.
1.4 The values stated in SI units are to be regarded as the standard.
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.
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Designation: D 7012 – 04
Standard Test Method for
Compressive Strength and Elastic Moduli of Intact Rock
Core Specimens under Varying States of Stress and
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
1.1.3 The original four standards are now referred to as
and confined compression. The tests provide data in determin-
Methods in this standard as follows: Method A (D2664)
ing the strength of rock, namely: the uniaxial strength, shear
Triaxial Compressive Strength of Undarined Rock Core Speci-
strengths at varying pressures and varying temperatures, angle
mens Without Pore Pressure Measurements; Method B
ofinternalfriction,(angleofshearingresistance),andcohesion
(D5407) Elastic Moduli of Undrained Rock Core Specimens in
intercept. The test method specifies the apparatus, instrumen-
Triaxial Compression Without Pore Pressure Measurements,
tation, and procedures for determining the stress-axial strain
Method C (D2938 Unconfined Compressive Strength of Intact
andthestress-lateralstraincurves,aswellasYoung’smodulus,
Rock Core Specimens; Method D (d3148) Elastic Moduli of
E,andPoisson’sratio, y.Itshouldbeobservedthatthismethod
Intact Rock Core Specimerns in Uniaxial Compression; and
makes no provision for pore pressure measurements and
Option A Elevated Temperatures.
specimens are undrained (platens are not vented). Thus the
1.2 For an isotropic material, the relation between the shear
strength values determined are in terms of total stress, that is,
and bulk moduli andYoung’s modulus and Poisson’s ratio are:
are not corrected for pore pressures. This test method does not
include the procedures necessary to obtain a stress-strain curve E
G 5 (1)
2~11y!
beyond the ultimate strength.
1.1.1 This standard replaces and combines the following
E
K 5 (2)
Standard Test Methods for: D 2664 Triaxial Compressive
3~1 2 2y!
Strength of Undrained Rock Core Specimens Without Pore
where:
Pressure Measurements; D 5407 Elastic Moduli of Undrained
G = shear modulus,
Rock Core Specimens in Triaxial Compression Without Pore
K = bulk modulus,
Pressure Measurements; D 2938 Unconfined Compressive
E = Young’s modulus, and
Strength of Intact Rock Core Specimens; and D 3148 Elastic
y = Poisson’s ratio.
Moduli of Intact Rock Core Specimens in Uniaxial Compres-
1.2.1 The engineering applicability of these equations de-
sion.
creases with increasing anisotropy of the rock. It is desirable to
1.1.2 The original four standards are now referred to as
conduct tests in the plane of foliation, cleavage or bedding and
Methods in this standard as follows: Method A — Triaxial
at right angles to it to determine the degree of anisotropy. It is
Compressive Strength of Undrained Rock Core Specimens
notedthatequationsdevelopedforisotropicmaterialsmaygive
Without Pore Pressure Measurements; Method B — Elastic
only approximate calculated results if the difference in elastic
Moduli of Undrained Rock Core Specimens in Triaxial Com-
moduli in two orthogonal directions is greater than 10 % for a
pression Without Pore Pressure Measurements; Method C —
given stress level.
Unconfined Compressive Strength of Intact Rock Core Speci-
NOTE 1—Elastic moduli measured by sonic methods (Test Method
D 2845) may often be employed as preliminary measures of anisotropy.
1.3 This test method given for determining the elastic
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
constants does not apply to rocks that undergo significant
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved Feb. 1, 2004. Published February 2004. inelastic strains during the test, such as potash and salt. The
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7012–04
elastic moduli for such rocks should be determined from underground rock masses exist. The elastic constants are used
unload-reload cycles, that are not covered by this test method. to calculate the stress and deformation in rock structures.
1.4 The values stated in SI units are to be regarded as the 4.3 The deformation and strength properties of rock cores
standard. measured in the laboratory usually do not accurately reflect
1.5 This standard does not purport to address all of the large-scale in situ properties because the latter are strongly
safety concerns, if any, associated with its use. It is the influenced by joints, faults, inhomogeneities, weakness planes,
responsibility of the user of this standard to establish appro- and other factors. Therefore, laboratory values for intact
priate safety and health practices and determine the applica- specimens must be employed with proper judgment in engi-
bility of regulatory limitations prior to use. neering applications.
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
are dependent on the competence of the personnel performing them , and
2.1 ASTM Standards:
on the suitability of the equipment and facilities used.Agencies that meet
D 653 Terminology Relating to Soil, Rock and Contained
the criteria of Practice D 3740 are generally considered capable of
Fluids
competent and objective testing. Users of this test method are cautioned
D 2216 TestMethodforLaboratoryDeterminationofWater
that compliance with Practice D 3740 does not in itself assure reliable
(Moisture) Content of Soil and Rock
testing. Reliable testing depends on many factors; Practice D 3740
D 2845 Test Method for Laboratory Determination of Pulse
provides a means for evaluating some of those factors.
Velocities and Ultrasonic Constants of Rock
5. Apparatus
D 3740 Practice for Minimum Requirements for Agencies
Engaged in the Testing and/or Inspection of Soil and Rock 5.1 Loading Device—The loading device shall be of suffi-
as Used in Engineering Design and Construction cient capacity to apply load at a rate conforming to the
D 4543 Practice for Preparing Rock Core Specimens and
requirements specified in 9.6. It shall be verified at suitable
Determining Dimensional and Shape Tolerances time intervals in accordance with the procedures given in
E 4 Practices for Force Verification of Testing Machines
Practices E 4 and comply with the requirements prescribed in
E 122 Practices for Choice of Sample Size to Estimate a the method. The loading device may be equipped with a
Measure of Quality for a Lot or Process
displacement transducer that can be used to advance the
E 691 Practices for Conducting an Interlaboratory Study to loading ram at a specified rate.
Determine the Precision of a Test Method
NOTE 3—If the load-measuring device is located outside the confining
compression apparatus, calibrations to determine the seal friction need to
3. Summary of Test Method
be made to ensure the accuracy specified in Practices E 4.
3.1 A rock core specimen is cut to length and the ends are
5.2 Confining Apparatus —The confined pressure appara-
machined flat. The specimen is placed in a loading frame and
tus shall consist of a chamber in which the test specimen may
if required, placed in a loading chamber and subjected to
besubjectedtoaconstantlateralfluidpressureandtherequired
confining pressure. In an elevated temperature test the speci-
axial load. The apparatus shall have safety valves, suitable
men is heated to the desired test temperature. Axial load is
entry ports for filling the chamber, and associated hoses, gages,
increased continuously on the specimen, and deformation is
and valves as needed.
measured as a function of load until peak load and failure are
5.3 Flexible Membrane—This membrane encloses the rock
obtained.
specimen and extends over the platens to prevent penetration
bytheconfiningfluid.Asleeveofnaturalorsyntheticrubberor
4. Significance and Use
plastic is satisfactory for room temperature tests; however,
metal or high-temperature rubber (for example, viton) jackets
4.1 The parameters obtained from these procedures are in
terms of undrained total stress (as already mentioned in 1.1.1.). are usually required for elevated temperature tests. The mem-
brane shall be inert relative to the confining fluid and shall
However, there are some cases where either the rock type or
the loading condition of the problem under consideration will cover small pores in the specimen without rupturing when
confining pressure is applied. Plastic or silicone rubber coat-
require the effective stress or drained parameters be deter-
mined. ings may be applied directly to the specimen provided these
materials do not penetrate and strengthen or weaken the
4.2 Unconfined compressive strength of rock is used in
many design formulas and is sometimes used as an index specimen. Care must be taken to form an effective seal where
the platen and specimen meet. Membranes formed by coatings
property to select the appropriate excavation technique. Defor-
mation and strength of rock are known to be functions of shall be subject to the same performance requirements as
elastic sleeve membranes.
confining pressure. The confined compression test is com-
monly used to simulate the stress conditions under which most 5.4 Pressure-Maintaining Device—Ahydraulic pump, pres-
sureintensifier,orothersystemshallhavesufficientcapacityto
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Assembly and detail drawings of an apparatus that meets these requirements
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM and which is designed to accommodate 2 ⁄8-in. (53.975-mm) diameter specimens
Standards volume information, refer to the standard’s Document Summary page on andoperateataconfiningfluidpressureof68.9Mpa(10 000psi)areavailablefrom
the ASTM website. Headquarters. Request Adjunct No. 12-426640-00.
D7012–04
maintain constant the desired lateral pressure. The pressuriza- platens are new and shall be maintained within a permissible
tion system shall be capable of maintaining the confining variation of 0.025 mm. The diameter of the spherical seat shall
pressure constant to within 61 % throughout the test. The be at least as large as that of the test specimen, but shall not
confining pressure shall be measured with a hydraulic pressure exceed twice the diameter of the test specimen. The center of
gage or electronic transducer having an accuracy of at least 61
the sphere in the spherical seat shall coincide with that of the
percent of the confining pressure, including errors due to bearing face of the specimen. The spherical seat shall be
readout equipment, and a resolution of at least 0.5 % of the
properly lubricated to assure free movement. The movable
confining pressure. portion of the platen shall be held closely in the spherical seat,
but the design shall be such that the bearing face can be rotated
5.5 Confining-Pressure Fluids—Forroomtemperaturetests,
and tilted through small angles in any direction. If a spherical
hydraulic fluids compatible with the pressure-maintaining
seatisnotused,thebearingfacesoftheblocksshallbeparallel
device shall be used. For elevated temperature tests, the fluid
to 0.0005 mm/mm of platen diameter. The platen diameter
must remain stable at the temperature and pressure levels
shall be at least as great as that of the specimen and have a
designated for the test.
length-to-diameter ratio of at least 1:2.
5.6 Elevated-Temperature Enclosure—The elevated tem-
5.9 Strain/Deformation Measuring Devices—The strain/
perature enclosure shall be either an internal system that fits
deformation measuring system shall measure the strain with a
inside the loading apparatus or the confining pressure appara-
-6
resolution of at least 25 3 10 strain and an accuracy within
tus, an external system enclosing the entire confining pressure
-6
2 % of the value of readings above 250 3 10 strain and
apparatus, or an external system encompassing the complete
accuracy and resolution within 5 3 10 -6 for readings lower
test apparatus. For high temperatures, a system of heaters,
-6
than 250 3 10 strain, including errors introduced by excita-
insulation, and temperature-measuring devices are normally
tion and readout equipment. The system shall be free from
required to maintain the specified temperature. Temperature
non-characterized long-term instability (drift) that results in an
shall be measured at three locations, with one sensor near the
-8
apparent strain of 10 /s or greater.
top,oneatmidheight,andonenearthebottomofthespecimen.
The “average” specimen temperature, based on the midheight
NOTE 5—The user is cautioned about the influence of pressure and
sensor, shall be maintained to within 61°C of the required test
temperatureontheoutputofstrainanddeformationsensorslocatedwithin
temperature. The maximum temperature difference between
the confining pressure apparatus.
the midheight sensor and either end sensor shall not exceed
5.9.1 Determination of Axial Strain—The axial deforma-
3°C.
tions or strains may be determined from data obtained by
NOTE 4—An alternative to measuring the temperature at three locations
electrical resistance strain gages, compressometers, linear vari-
along the specimen during the test is to determine the temperature
able differential transformers (LVDTs), or other suitable
distribution in a specimen that has temperature sensors located in drill
means. The design of the measuring device shall be such that
holes at a minimum of six positions: along both the centerline and
the average of at least two axial strain measurements can be
specimen periphery at midheight and each end of the specimen. The
determined. Measuring positions shall be equally spaced
specimen may originate from the same batch as the test specimens and
around the circumference of the specimen, close to midheight.
conform to the same dimensional tolerances and to the same degree of
intactness. The temperature controller set point may be adjusted to obtain
The gage length over which the axial strains are determined
steady-state temperatures in the specimen that meet the temperature
shall be at least ten grain diameters in magnitude.
requirements at each test temperature (the centerline temperature at
5.9.
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