ASTM D7012-23

Standard Test Methods for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures

SIGNIFICANCE AND USE
5.1 The parameters obtained from Methods A and B are in terms of undrained total stress. 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.  
5.2 Method C, uniaxial 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. Method A, triaxial compression test, is commonly used to simulate the stress conditions under which most underground rock masses exist. The elastic constants (Methods B and D) are used to calculate the stress and deformation in rock structures.  
5.3 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, inhomogeneity, weakness planes, and other factors. Therefore, laboratory values for intact specimens shall be employed with proper judgment in engineering applications.
Note 2: 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. Users of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means for evaluating some of those factors.
SCOPE
1.1 These four test methods cover the determination of the strength of intact rock core specimens in uniaxial and triaxial compression. Methods A and B determine the triaxial compressive strength at different pressures and Methods C and D determine the unconfined, uniaxial strength.  
1.2 Methods A and B can be used to determine the angle of internal friction, angle of shearing resistance, and cohesion intercept.  
1.3 Methods B and D specify 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, υ. These methods do not make provisions for pore pressure measurements and specimens are undrained (platens are not vented). Thus, the strength values determined are in terms of total stress and are not corrected for pore pressures. These test methods do not include the procedures necessary to obtain a stress-strain curve beyond the ultimate strength.  
1.4 Option A allows for testing at different temperatures and can be applied to any of the test methods, if requested.  
1.5 This standard replaces and combines the following Standard Test Methods: D2664 Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements; D5407 Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure Measurements; D2938 Unconfined Compressive Strength of Intact Rock Core Specimens; and D3148 Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression. The original four standards are now referred to as Methods in this standard.  
1.5.1 Method A—Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements.
1.5.1.1 Method A requires strength determination only. Strain measurements and a stress-strain curve are not required.  
1.5.2 Method B—Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure Measurements.  
1.5.3 Method C—Uniaxial Compressive Strength of Intact Rock Core Specimens.
1.5.3.1 Method C requires strength determination only. Strain measurements and a stress-strain curve are not required.  
1.5.4 Method D—Elastic Moduli of Intact Rock Core Specimens in Uniax...

General Information

• Status: Published
• Publication Date: 14-Jun-2023
• ICS: 13.080.20 - Physical properties of soils
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.12 - Rock Mechanics

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM E122-09e1 - Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
• Effective Date: 01-Aug-2011
• Refers: ASTM D2216-10 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Jul-2010
• Refers: ASTM E4-10 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2010
• Refers: ASTM D3740-10 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2010
• Refers: ASTM E4-09a - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Nov-2009
• Refers: ASTM E122-09 - Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
• Effective Date: 01-Aug-2009

Overview

ASTM D7012-23: Standard Test Methods for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures sets out comprehensive methods for determining the compressive strength and elastic moduli of rock core specimens. Developed by ASTM International's Committee D18 on Soil and Rock, this standard is key for professionals in geotechnical engineering, civil engineering, mining, and construction who require reliable laboratory data on the mechanical properties of rock.

This standard consolidates and enhances previous standards (ASTM D2664, D5407, D2938, and D3148), providing unified and updated guidance for testing under various stress and temperature conditions. ASTM D7012-23 ensures consistency in assessing rock behavior, which is critical in engineering design and safety.

Key Topics

• Test Methods: The standard outlines four primary methods:

  • 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.
  • Method C: Uniaxial compressive strength of intact rock core specimens.
  • Method D: Elastic moduli of intact rock core specimens in uniaxial compression.

• Stress and Strain Measurement:

  • Focus on determining compressive strength and elastic properties (such as Young’s modulus and Poisson’s ratio) under both confined (triaxial) and unconfined (uniaxial) conditions.
  • Laboratory results are based on undrained total stress as specimens are not vented for pore pressure.

• Temperature Variation:

  • Option A allows for tests at temperatures above or below room temperature, which can be applied across all methods if requested.

• Limitations:

  • Results from laboratory tests may not fully represent in situ rock mass properties due to features like joints or faults.
  • Emphasis on professional judgment when applying data from intact specimens to engineering problems.

• Quality and Safety:

  • Importance of using competent personnel, adequate equipment, and adherence to established practices (such as ASTM D3740).

Applications

ASTM D7012-23 is widely used for:

• Engineering Design:

  • Provides critical data for designing tunnels, slopes, foundations, and other structures interacting with rock masses.
  • Uniaxial compressive strength is commonly used in design formulas and as an index property for selecting excavation techniques.

• Rock Mechanics and Geotechnics:

  • Assessment of rock deformation and strength properties helps understand the behavior of underground rock masses and supports risk management in projects like mining or dam construction.

• Material Characterization:

  • Determines elastic constants needed for stress and deformation calculations in structural analyses.

• Research and Quality Control:

  • Supports geological investigations and validation of rock properties for construction aggregate, stability assessments, and academic research.

Related Standards

To ensure comprehensive testing and reporting, consider the following ASTM standards:

• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D2216: Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock
• ASTM D3740: Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock
• ASTM D4543: Practices for Preparing Rock Core as Cylindrical Test Specimens and Verifying Conformance to Dimensional and Shape Tolerances
• ASTM D6026: Practice for Using Significant Digits and Data Records in Geotechnical Data
• ASTM E4: Practices for Force Calibration and Verification of Testing Machines
• ASTM E122: Practice for Calculating Sample Size to Estimate the Average for a Lot or Process

ASTM D7012-23 is a foundational reference for laboratory rock mechanics testing, instrumental in generating reliable geotechnical data for safe and effective engineering solutions.

Standards Content (Sample)

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: D7012 − 23
Standard Test Methods 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 D7012; 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* 1.5.1.1 Method A requires strength determination only.
Strain measurements and a stress-strain curve are not required.
1.1 These four test methods cover the determination of the
1.5.2 Method B—Elastic Moduli of Undrained Rock Core
strength of intact rock core specimens in uniaxial and triaxial
Specimens in Triaxial Compression Without Pore Pressure
compression. Methods A and B determine the triaxial compres-
Measurements.
sive strength at different pressures and Methods C and D
1.5.3 Method C—Uniaxial Compressive Strength of Intact
determine the unconfined, uniaxial strength.
Rock Core Specimens.
1.2 Methods A and B can be used to determine the angle of
1.5.3.1 Method C requires strength determination only.
internal friction, angle of shearing resistance, and cohesion
Strain measurements and a stress-strain curve are not required.
intercept.
1.5.4 Method D—Elastic Moduli of Intact Rock Core Speci-
1.3 Methods B and D specify the apparatus,
mens in Uniaxial Compression.
instrumentation, and procedures for determining the stress-
1.5.5 Option A: Temperature Variation—Applies to any of
axial strain and the stress-lateral strain curves, as well as
the methods and allows for testing at temperatures above or
Young’s modulus, E, and Poisson’s ratio, υ. These methods do
below room temperature.
not make provisions for pore pressure measurements and
1.6 For an isotropic material in Test Methods B and D, the
specimens are undrained (platens are not vented). Thus, the
relation between the shear and bulk moduli and Young’s
strength values determined are in terms of total stress and are
modulus and Poisson’s ratio are:
not corrected for pore pressures. These test methods do not
E
include the procedures necessary to obtain a stress-strain curve
G 5 (1)
2~11υ!
beyond the ultimate strength.
E
1.4 Option A allows for testing at different temperatures and
K 5 (2)
3 1 2 2υ
~ !
can be applied to any of the test methods, if requested.
where:
1.5 This standard replaces and combines the following
Standard Test Methods: D2664 Triaxial Compressive Strength
G = shear modulus,
of Undrained Rock Core Specimens Without Pore Pressure K = bulk modulus,
Measurements; D5407 Elastic Moduli of Undrained Rock Core E = Young’s modulus, and
υ = Poisson’s ratio.
Specimens in Triaxial Compression Without Pore Pressure
Measurements; D2938 Unconfined Compressive Strength of
1.6.1 The engineering applicability of these equations de-
Intact Rock Core Specimens; and D3148 Elastic Moduli of
creases with increasing anisotropy of the rock. It is desirable to
Intact Rock Core Specimens in Uniaxial Compression. The
conduct tests in the plane of foliation, cleavage or bedding and
original four standards are now referred to as Methods in this
at right angles to it to determine the degree of anisotropy. It is
standard.
noted that equations developed for isotropic materials may give
1.5.1 Method A—Triaxial Compressive Strength of Und-
only approximate calculated results if the difference in elastic
rained Rock Core Specimens Without Pore Pressure Measure-
moduli in two orthogonal directions is greater than 10 % for a
ments.
given stress level.
1 NOTE 1—Elastic moduli measured by sonic methods (Test Method
These test methods are under the jurisdiction of ASTM Committee D18 on Soil
D2845) may often be employed as a preliminary measure of anisotropy.
and Rock and is the direct responsibility of Subcommittee D18.12 on Rock
Mechanics.
1.7 Test Methods B and D for determining the elastic
Current edition approved June 15, 2023. Published June 2023. Originally
ɛ1
constants do not apply to rocks that undergo significant
approved in 2004. Last previous edition approved in 2014 as D7012 – 14 . DOI:
10.1520/D7012-23. inelastic strains during the test, such as potash and salt. The
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7012 − 23
elastic moduli for such rocks should be determined from E122 Practice for Calculating Sample Size to Estimate, With
unload-reload cycles that are not covered by these test meth- Specified Precision, the Average for a Characteristic of a
ods. Lot or Process
2.2 ASTM Adjunct:
1.8 The values stated in SI units are to be regarded as
Triaxial Compression Chamber Drawings (3)
standard. No other units of measurement are included in this
standard. Reporting of test results in units other than SI shall
3. Terminology
not be regarded as nonconformance with this test method.
3.1 Definitions:
1.9 All observed and calculated values shall conform to the
3.1.1 For definitions of common technical terms in this
guidelines for significant digits and rounding established in
standard, refer to Terminology D653.
Practice D6026.
1.9.1 The procedures used to specify how data are collected/
4. Summary of Test Methods
recorded or calculated, in this standard are regarded as the
4.1 A rock core specimen is cut to length and the ends are
industry standard. In addition, they are representative of the
machined flat. The specimen is placed in a loading frame and
significant digits that generally should be retained. The proce-
if necessary, placed in a loading chamber and subjected to
dures used do not consider material variation, purpose for
confining pressure. For a specimen tested at a different
obtaining the data, special purpose studies, or any consider-
temperature, the test specimen is heated or cooled to the
ations for the user’s objectives; and it is common practice to
desired test temperature prior to the start of the test. The axial
increase or reduce significant digits of reported data to be
load on the specimen is then increased and measured until the
commensurate with these considerations. It is beyond the scope
specimen fails. Deformation measurements are not required for
of this standard to consider significant digits used in analytical
Methods A and C. For Methods B and D, deformations are
methods for engineering design.
measured as a function of load until peak load and failure are
1.10 This standard does not purport to address all of the
obtained.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety, health, and environmental practices and deter-
5.1 The parameters obtained from Methods A and B are in
mine the applicability of regulatory limitations prior to use.
terms of undrained total stress. However, there are some cases
1.11 This international standard was developed in accor-
where either the rock type or the loading condition of the
dance with internationally recognized principles on standard-
problem under consideration will require the effective stress or
ization established in the Decision on Principles for the
drained parameters be determined.
Development of International Standards, Guides and Recom-
5.2 Method C, uniaxial compressive strength of rock is used
mendations issued by the World Trade Organization Technical
in many design formulas and is sometimes used as an index
Barriers to Trade (TBT) Committee.
property to select the appropriate excavation technique. Defor-
2. Referenced Documents
mation and strength of rock are known to be functions of
2.1 ASTM Standards: confining pressure. Method A, triaxial compression test, is
D653 Terminology Relating to Soil, Rock, and Contained commonly used to simulate the stress conditions under which
Fluids most underground rock masses exist. The elastic constants
D2216 Test Methods for Laboratory Determination of Water (Methods B and D) are used to calculate the stress and
(Moisture) Content of Soil and Rock by Mass deformation in rock structures.
D2845 Test Method for Laboratory Determination of Pulse
5.3 The deformation and strength properties of rock cores
Velocities and Ultrasonic Elastic Constants of Rock
measured in the laboratory usually do not accurately reflect
(Withdrawn 2017)
large-scale in situ properties because the latter are strongly
D3740 Practice for Minimum Requirements for Agencies
influenced by joints, faults, inhomogeneity, weakness planes,
Engaged in Testing and/or Inspection of Soil and Rock as
and other factors. Therefore, laboratory values for intact
Used in Engineering Design and Construction
specimens shall be employed with proper judgment in engi-
D4543 Practices for Preparing Rock Core as Cylindrical Test
neering applications.
Specimens and Verifying Conformance to Dimensional
NOTE 2—The quality of the result produced by this standard is
and Shape Tolerances dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the
D6026 Practice for Using Significant Digits and Data Re-
criteria of Practice D3740 are generally considered capable of competent
cords in Geotechnical Data
and objective testing. Users of this standard are cautioned that compliance
E4 Practices for Force Calibration and Verification of Test-
with Practice D3740 does not in itself ensure reliable results. Reliable
ing Machines
results depend on many factors; Practice D3740 provides a means for
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Assembly and detail drawings of an apparatus that meets these requirements
Standards volume information, refer to the standard’s Document Summary page on and which is designed to accommodate 54-mm diameter specimens and operate at
the ASTM website. a confining fluid pressure of 68.9 MPa are available from ASTM International
The last approved version of this historical standard is referenced on Headquarters. Order Adjunct No. ADJD7012-E-PDF. Original adjunct produced in
www.astm.org. 1982.
D7012 − 23
evaluating some of those factors.
should remain stable at the temperature and pressure levels
designated for the test.
6. Apparatus
6.2.2 Option A:
6.1 Compression Apparatus:
6.2.2.1 Temperature Enclosure—The temperature enclosure
6.1.1 Methods A to D:
shall be either an internal system that fits inside the loading
6.1.1.1 Loading Device—The loading device shall be of
apparatus or the confining pressure apparatus, an external
sufficient capacity to apply load at a rate conforming to the
system enclosing the entire confining pressure apparatus, or an
requirements specified in 9.4.1. It shall be verified at suitable
external system encompassing the complete test apparatus. For
time intervals in accordance with the procedures given in
high or low temperatures, a system of heaters or coolers,
Practices E4 and comply with the requirements prescribed in
respectively, insulation, and temperature-measuring devices
the method. The loading device may be equipped with a
are normally necessary to maintain the specified temperature.
displacement transducer that can be used to advance the
Temperature shall be measured at three locations, with one
loading ram at a specified rate.
sensor near the top, one at mid-height, and one near the bottom
of the specimen. The “average” specimen temperature, based
NOTE 3—For Methods A and B, if the load-measuring device is located
on the mid-height sensor, shall be maintained to within 61°C
outside the confining compression apparatus, calibrations to determine the
of the specified test temperature. The maximum temperature
seal friction need to be made to make sure the loads measured meet the
accuracy specified in Practices E4.
difference between the mid-height sensor and either end sensor
NOTE 4—The failure strain and mode of failure observed during testing
shall not exceed 3°C.
can be affected by the stiffness of the load frame used for testing compared
to the stiffness of the tested specimen.
NOTE 6—An alternative to measuring the temperature at three locations
along the specimen during the test is to determine the temperature
6.2 Confining System:
distribution in a specimen that has temperature sensors located in drill
6.2.1 Methods A and B:
holes at a minimum of six positions: along both the centerline and
6.2.1.1 Confining Apparatus —The confining pressure ap-
specimen periphery at mid-height and each end of the specimen. The
paratus shall consist of a chamber in which the test specimen
specimen may originate from the same batch as the test specimens and
conform to the same dimensional tolerances and to the same degree of
may be subjected to a constant lateral fluid pressure and the
intactness. The temperature controller set point may be adjusted to obtain
requested axial load. The apparatus shall have safety valves,
steady-state temperatures in the specimen that meet the temperature
suitable entry ports for filling the chamber, and associated
requirements at each test temperature. The centerline temperature at
hoses, gages, and valves as needed.
mid-height may be within 61°C of the specified test temperature and all
6.2.1.2 Flexible Membrane—This membrane encloses the
other specimen temperatures may not deviate from this temperature by
more than 3°C. The relationship between controller set point and
rock specimen and extends over the platens to prevent penetra-
specimen temperature can be used to determine the specimen temperature
tion by the confining fluid. A sleeve of natural or synthetic
during testing provided that the output of the temperature feedback sensor
rubber or plastic is satisfactory for room temperature tests;
or other fixed-location temperature sensor in the triaxial apparatus is
however, metal or high-temperature rubber (fluoroelastomer)
maintained constant within 61°C of the specified test temperature. The
jackets are usually necessary for elevated temperature tests relationship between temperature controller set point and steady-state
specimen temperature may be verified periodically. The specimen is used
(Note 5). The membrane shall be inert relative to the confining
solely to determine the temperature distribution in a specimen in the
fluid and shall cover small pores in the specimen without
triaxial apparatus. It is not to be used to determine compressive strength
rupturing when confining pressure is applied. Plastic or sili-
or elastic constants.
cone rubber coatings may be applied directly to the specimen
6.2.2.2 Temperature Measuring Device—Special limits-of-
provided these materials do not penetrate and strengthen or
error thermocouples or platinum resistance thermometers
weaken the specimen. Care shall be taken to form an effective
(RTDs) having minimum accuracies of 61°C with a resolution
seal where the platen and specimen meet. Membranes formed
of 0.1°C shall be used.
by coatings shall be subject to the same performance require-
6.2.3 Bearing Surfaces:
ments as elastic sleeve membranes.
6.2.3.1 Methods A to D:
NOTE 5—The properties of flexible membranes at room temperature
(1) Platens—Two steel platens are used to transmit the
and elevated temperatures are not considered significant to the test.
axial load to the ends of the specimen. They shall be made of
However, the properties of flexible membranes at low temperatures should
be known and the effect on results be compensated for if they impact the
tool-hardened steel to a minimum Rockwell Hardness of 58 on
result.
the “C” scale. One of the platens shall be spherically seated and
6.2.1.3 Pressure-Maintaining Device—A hydraulic pump, the other shall be a plain rigid platen. The bearing faces shall
pressure intensifier, or other system having sufficient capacity not depart from a plane by more than 0.015 mm when the
to maintain the desired lateral pressure to within 61 % platens are new and shall be maintained within a permissible
throughout the test. The confining pressure shall be measured variation of 0.025 mm. The diameter of the spherical seat shall
with a hydraulic pressure gauge or electronic transducer having be at least as large as that of the test specimen, but shall not
a minimum accuracy of 1 % of the confining pressure, includ- exceed twice the diameter of the test specimen. The center of
ing errors due to readout equipment, and a minimum resolution the sphere in the spherical seat shall coincide with that of the
of 0.5 % of the confining pressure. bearing face of the specimen. The spherical seat shall be
6.2.1.4 Confining-Pressure Fluids—Hydraulic fluids com- properly lubricated to allow free movement. The movable
patible with the pressure-maintaining device and flexible portion of the platen shall be held closely in the spherical seat,
membranes shall be used. For tests using Option A, the fluid but the design shall be such that the bearing face can be rotated
D7012 − 23
and tilted through small angles in any direction. If a spherical 7.3 Elevated temperatures increase the risks of electrical
seat is not used, the bearing surfaces shall be parallel to 0.0005 shorts and fire. The flash point of the confining pressure fluid
mm/mm of platen diameter. The platen diameter shall be at shall be above the operating temperatures during the test.
least as great as that of the specimen and have a thickness-to-
8. Test Specimens
diameter ratio of at least 1:2.
8.1 Specimen Selection—The specimens for each sample
6.3 Deformation Devices:
shall be selected from cores representing a valid average of the
6.3.1 Methods B and D:
type of rock under consideration. This sample selection can be
6.3.1.1 Strain/Deformation Measuring Devices—
achieved by visual observations of mineral constituents, grain
Deformations or strains may be determined from data obtained
sizes and shape, partings and defects such as pores and fissures,
by electrical resistance strain gages, compressometers, linear
or by other methods such as ultrasonic velocity measurements.
variable differential transformers (LVDTs), or other suitable
The minimum diameter of rock test specimens shall be ten
means. The strain/deformation measuring system shall mea-
-6
times the diameter of the largest mineral grain. For weak rock
sure the strain with a minimum resolution of 25 × 10 strain
types, which behave more like soil, for example, weakly
and an accuracy within 2 % of the value of readings above 250
-6 -6
cemented sandstone, the minimum specimen diameter shall be
× 10 strain and accuracy and resolution within 5 × 10 for
-6
six times the maximum particle diameter. The specified mini-
readings lower than 250 × 10 strain, including errors intro-
mum specimen diameter of approximately 47 mm satisfy this
duced by excitation and readout equipment. The system shall
criterion in the majority of cases. When cores of diameter
be free from non-characterized long-term instability (drift) that
-8
smaller than the specified minimum must be tested because of
results in an apparent strain of 10 /s or greater.
the unavailability of larger diameter core, as is often the case in
NOTE 7—The user is cautioned about the influence of pressure and
the mining industry, suitable notation of this fact shall be made
temperature on the output of strain and deformation sensors located within
in the report.
the confining pressure apparatus.
8.1.1 Desirable specimen length to diameter ratios are
6.3.1.2 Determination of Axial Strain—The design of the
between 2.0:1 and 2.5:1. Specimen length to diameter ratios of
measuring device shall be such that the average of two or more
less than 2.0:1 are unacceptable. If it is necessary to test
axial strain measurements can be determined. Measuring
specimens not meeting the length to diameter ratio require-
positions shall be equally spaced around the circumference of
ments due to lack of available specimens, the report shall
the specimen, close to midheight. The minimum gauge length
contain a note stating the non-conformance with this standard
over which the axial strains are determined shall be ten grain
including a statement explaining that the results may differ
diameters in magnitude.
from results obtained from a test specimen that meets the
6.3.1.3 Determination of Lateral Strain—The lateral defor-
requirements. Laboratory specimen length to diameter ratios
mations or strains may be measured by any of the methods
must be employed with proper judgment in engineering appli-
mentioned in 6.3.1.1. Either circumferential or diametric de-
cations.
formations or strains may be measured. A single transducer that
8.1.2 The number of specimens necessary to obtain a
wraps around the specimen can be used to measure the change
specific level of statistical results may be determined using Test
in circumference. A minimum of two diametric deformation
Method E122. However, it may not be economically practi-
sensors shall be used if diametric deformations are measured.
cable to achieve a specific confidence level and professional
These sensors shall be equally spaced around the circumfer-
judgment may be necessary.
ence of the specimen close to midheight. The average defor-
mation or strain from the diametric sensors shall be recorded. 8.2 Preparation—Test specimens shall be prepared in ac-
cordance with Practice D4543.
NOTE 8—The use of strain gauge adhesives requiring cure temperatures
8.2.1 Test results for specimens not meeting the require-
above 65°C is not allowed unless it is known that microfractures do not
ments of Practice D4543 shall contain a note describing the
develop and mineralogical changes do not occur at the cure temperature.
non-conformance and a statement explaining that the results
6.4 Timing Devices—A clock, stopwatch, digital timer, or
reported may differ from results obtained from a test specimen
similar readable to 1 minute.
that meets the requirements of Practice D4543.
7. Safety Hazards
8.3 Moisture condition of the specimen at the time of test
7.1 Danger exists near confining pressure testing equipment
can have a significant effect upon the deformation of the rock.
because of the high pressures and loads developed within the
Good practice generally dictates that laboratory tests shall be
system. Test systems shall be designed and constructed with
made upon specimens representative of field conditions. Thus,
adequate safety factors, assembled with fittings rated for the
it follows that the field moisture condition of the specimen
pressure to be used, and provided with protective shields to
shall be preserved until the time of test. On the other hand,
pro
...

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.
´1
Designation: D7012 − 14 D7012 − 23
Standard Test Methods 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 D7012; 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.
ε NOTE—Editorially corrected legend for Eq 3 in August 2017.
1. Scope Scope*
1.1 These four test methods cover the determination of the strength of intact rock core specimens in uniaxial and triaxial
compression. Methods A and B determine the triaxial compressive strength at different pressures and Methods C and D determine
the unconfined, uniaxial strength.
1.2 Methods A and B can be used to determine the angle of internal friction, angle of shearing resistance, and cohesion intercept.
1.3 Methods B and D specify 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, υ. These methods make no provision do not make
provisions for pore pressure measurements and specimens are undrained (platens are not vented). Thus, the strength values
determined are in terms of total stress and are not corrected for pore pressures. These test methods do not include the procedures
necessary to obtain a stress-strain curve beyond the ultimate strength.
1.4 Option A allows for testing at different temperatures and can be applied to any of the test methods, if requested.
1.5 This standard replaces and combines the following Standard Test Methods: D2664 Triaxial Compressive Strength of
Undrained Rock Core Specimens Without Pore Pressure Measurements; D5407 Elastic Moduli of Undrained Rock Core
Specimens in Triaxial Compression Without Pore Pressure Measurements; D2938 Unconfined Compressive Strength of Intact
Rock Core Specimens; and D3148 Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression. The original four
standards are now referred to as Methods in this standard.
1.5.1 Method A: A—Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements.
1.5.1.1 Method A is used for obtaining strength determinations. Strain is not typically measured; therefore requires strength
determination only. Strain measurements and a stress-strain curve is not produced.are not required.
1.5.2 Method B: B—Elastic Moduli of Undrained Rock Core Specimens in Triaxial Compression Without Pore Pressure
Measurements.
These test methods are under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved May 1, 2014June 15, 2023. Published June 2014June 2023. Originally approved in 2004. Last previous edition approved in 20132014 as D7012
ɛ1
– 13.14 . DOI: 10.1520/D7012-14E01.10.1520/D7012-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7012 − 23
1.5.3 Method C: C—Uniaxial Compressive Strength of Intact Rock Core Specimens.
1.5.3.1 Method C is used for obtaining strength determinations. Strain is not typically measured; therefore requires strength
determination only. Strain measurements and a stress-strain curve is not produced.are not required.
1.5.4 Method D: D—Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression.
1.5.5 Option A: Temperature Variation—Applies to any of the methods and allows for testing at temperatures above or below room
temperature.
1.6 For an isotropic material in Test Methods B and D, the relation between the shear and bulk moduli and Young’s modulus and
Poisson’s ratio are:
E
G 5 (1)
2 11υ
~ !
E
K 5 (2)
3~12 2υ!
where:
G = shear modulus,
K = bulk modulus,
E = Young’s modulus, and
υ = Poisson’s ratio.
1.6.1 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 D2845) may often be employed as a preliminary measure of anisotropy.
1.7 Test Methods B and D for determining the elastic constants do 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 these test methods.
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.
1.9 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.9.1 The procedures used to specify how data are collected/recorded or calculated, 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 variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives;
and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design.
1.10 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.11 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.
D7012 − 23
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D2845 Test Method for Laboratory Determination of Pulse Velocities and Ultrasonic Elastic Constants of Rock (Withdrawn
2017)
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4543 Practices for Preparing Rock Core as Cylindrical Test Specimens and Verifying Conformance to Dimensional and Shape
Tolerances
D6026 Practice for Using Significant Digits and Data Records in Geotechnical Data
E4 Practices for Force Calibration and Verification of Testing Machines
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
2.2 ASTM Adjunct:
Triaxial Compression Chamber Drawings (3)
3. Terminology
3.1 Definitions:
3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.
4. Summary of Test MethodMethods
4.1 A rock core specimen is cut to length and the ends are machined flat. The specimen is placed in a loading frame and if
necessary, placed in a loading chamber and subjected to confining pressure. For a specimen tested at a different temperature, the
test specimen is heated or cooled to the desired test temperature prior to the start of the test. The axial load on the specimen is
then increased and measured continuously. until the specimen fails. Deformation measurements are not obtainedrequired for
Methods A and C, and C. For Methods B and D, deformations are measured as a function of load until peak load and failure are
obtained for Methods B and D.obtained.
5. Significance and Use
5.1 The parameters obtained from Methods A and B are in terms of undrained total stress. 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.
5.2 Method C, uniaxial 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.
Method A, triaxial compression test, is commonly used to simulate the stress conditions under which most underground rock
masses exist. The elastic constants (Methods B and D) are used to calculate the stress and deformation in rock structures.
5.3 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, inhomogeneity, weakness planes, and other factors.
Therefore, laboratory values for intact specimens mustshall be employed with proper judgment in engineering applications.
NOTE 2—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. Users
of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors;
Practice D3740 provides a means for evaluating some of those factors.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Assembly and detail drawings of an apparatus that meets these requirements and which is designed to accommodate 54-mm diameter specimens and operate at a confining
fluid pressure of 68.9 MPa are available from ASTM International Headquarters. Order Adjunct No. ADJD7012ADJD7012-E-PDF. Original adjunct produced in 1982.
D7012 − 23
6. Apparatus
6.1 Compression Apparatus:
6.1.1 Methods A to D:
6.1.1.1 Loading Device—The loading device shall be of sufficient capacity to apply load at a rate conforming to the requirements
specified in 9.4.1. It shall be verified at suitable time intervals in accordance with the procedures given in Practices E4 and comply
with the requirements prescribed in the method. The loading device may be equipped with a displacement transducer that can be
used to advance the loading ram at a specified rate.
NOTE 3—For Methods A and B, if the load-measuring device is located outside the confining compression apparatus, calibrations to determine the seal
friction need to be made to make sure the loads measured meet the accuracy specified in Practices E4.
NOTE 4—The failure strain and mode of failure observed during testing can be affected by the stiffness of the load frame used for testing compared to
the stiffness of the tested specimen.
6.2 Confining System:
6.2.1 Methods A and B:
6.2.1.1 Confining Apparatus —The confining pressure apparatus shall consist of a chamber in which the test specimen may be
subjected to a constant lateral fluid pressure and the requiredrequested axial load. The apparatus shall have safety valves, suitable
entry ports for filling the chamber, and associated hoses, gages, and valves as needed.
6.2.1.2 Flexible Membrane—This membrane encloses the rock specimen and extends over the platens to prevent penetration by
the confining fluid. A sleeve of natural or synthetic rubber or plastic is satisfactory for room temperature tests; however, metal or
high-temperature rubber (viton)(fluoroelastomer) jackets are usually necessary for elevated temperature tests. tests (Note 5). The
membrane shall be inert relative to the confining fluid and shall cover small pores in the specimen without rupturing when
confining pressure is applied. Plastic or silicone rubber coatings may be applied directly to the specimen provided these materials
do not penetrate and strengthen or weaken the specimen. Care mustshall be taken to form an effective seal where the platen and
specimen meet. Membranes formed by coatings shall be subject to the same performance requirements as elastic sleeve
membranes.
NOTE 5—The properties of flexible membranes at room temperature and elevated temperatures are not considered significant to the test. However, the
properties of flexible membranes at low temperatures should be known and the effect on results be compensated for if they impact the result.
6.2.1.3 Pressure-Maintaining Device—A hydraulic pump, pressure intensifier, or other system having sufficient capacity to
maintain the desired lateral pressure to within 61 % throughout the test. The confining pressure shall be measured with a hydraulic
pressure gauge or electronic transducer having an a minimum accuracy of at least 61 % 1 % of the confining pressure, including
errors due to readout equipment, and a minimum resolution of at least 0.5 % of the confining pressure.
6.2.1.4 Confining-Pressure Fluids—Hydraulic fluids compatible with the pressure-maintaining device and flexible membranes
shall be used. For tests using Option A, the fluid mustshould remain stable at the temperature and pressure levels designated for
the test.
6.2.2 Option A:
6.2.2.1 Temperature Enclosure—The temperature enclosure shall be either an internal system that fits inside the loading apparatus
or the confining pressure apparatus, an external system enclosing the entire confining pressure apparatus, or an external system
encompassing the complete test apparatus. For high or low temperatures, a system of heaters or coolers, respectively, insulation,
and temperature-measuring devices are normally necessary to maintain the specified temperature. Temperature shall be measured
at three locations, with one sensor near the top, one at mid-height, and one near the bottom of the specimen. The “average”
specimen temperature, based on the mid-height sensor, shall be maintained to within 61°C of the specified test temperature. The
maximum temperature difference between the mid-height sensor and either end sensor shall not exceed 3°C.
NOTE 6—An alternative to measuring the temperature at three locations along the specimen during the test is to determine the temperature distribution
in a specimen that has temperature sensors located in drill holes at a minimum of six positions: along both the centerline and specimen periphery at
D7012 − 23
mid-height and each end of the specimen. The specimen may originate from the same batch as the test specimens and conform to the same dimensional
tolerances and to the same degree of intactness. The temperature controller set point may be adjusted to obtain steady-state temperatures in the specimen
that meet the temperature requirements at each test temperature. The centerline temperature at mid-height may be within 61°C of the specified test
temperature and all other specimen temperatures may not deviate from this temperature by more than 3°C. The relationship between controller set point
and specimen temperature can be used to determine the specimen temperature during testing provided that the output of the temperature feedback sensor
or other fixed-location temperature sensor in the triaxial apparatus is maintained constant within 61°C of the specified test temperature. The relationship
between temperature controller set point and steady-state specimen temperature may be verified periodically. The specimen is used solely to determine
the temperature distribution in a specimen in the triaxial apparatus. It is not to be used to determine compressive strength or elastic constants.
6.2.2.2 Temperature Measuring Device—Special limits-of-error thermocouples or platinum resistance thermometers (RTDs)
having minimum accuracies of at least 61°C with a resolution of 0.1°C shall be used.
6.2.3 Bearing Surfaces:
6.2.3.1 Methods A to D:
(1) Platens—Two steel platens are used to transmit the axial load to the ends of the specimen. They shall be made of
tool-hardened steel to a minimum Rockwell Hardness of 58 on the “C” scale. One of the platens shall be spherically seated and
the other shall be a plain rigid platen. The bearing faces shall not depart from a plane by more than 0.015 mm when the platens
are new and shall be maintained within a permissible variation of 0.025 mm. The diameter of the spherical seat shall be at least
as large as that of the test specimen, but shall not exceed twice the diameter of the test specimen. The center of the sphere in the
spherical seat shall coincide with that of the bearing face of the specimen. The spherical seat shall be properly lubricated to allow
free movement. The movable 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 and tilted through small angles in any direction. If a spherical seat is not used, the bearing surfaces
shall be parallel to 0.0005 mm/mm of platen diameter. The platen diameter shall be at least as great as that of the specimen and
have a thickness-to-diameter ratio of at least 1:2.
6.3 Deformation Devices:
6.3.1 Methods B and D:
6.3.1.1 Strain/Deformation Measuring Devices—Deformations or strains may be determined from data obtained by electrical
resistance strain gages, compressometers, linear variable differential transformers (LVDTs), or other suitable means. The
-6
strain/deformation measuring system shall measure the strain with a minimum resolution of at least 25 × 10 strain and an
-6 -6
accuracy within 2 % of the value of readings above 250 × 10 strain and accuracy and resolution within 5 × 10 for readings lower
-6
than 250 × 10 strain, including errors introduced by excitation and readout equipment. The system shall be free from
-8
non-characterized long-term instability (drift) that results in an apparent strain of 10 /s or greater.
NOTE 7—The user is cautioned about the influence of pressure and temperature on the output of strain and deformation sensors located within the confining
pressure apparatus.
6.3.1.2 Determination of Axial Strain—The design of the measuring device shall be such that the average of at least twotwo or
more axial strain measurements can be determined. Measuring positions shall be equally spaced around the circumference of the
specimen, close to midheight. The minimum gauge length over which the axial strains are determined shall be at least ten grain
diameters in magnitude.
6.3.1.3 Determination of Lateral Strain—The lateral deformations or strains may be measured by any of the methods mentioned
in 6.3.1.1. Either circumferential or diametric deformations or strains may be measured. A single transducer that wraps around the
specimen can be used to measure the change in circumference. At least A minimum of two diametric deformation sensors shall
be used if diametric deformations are measured. These sensors shall be equally spaced around the circumference of the specimen
close to midheight. The average deformation or strain from the diametric sensors shall be recorded.
NOTE 8—The use of strain gauge adhesives requiring cure temperatures above 65°C is not allowed unless it is known that microfractures do not develop
and mineralogical changes do not occur at the cure temperature.
6.4 Timing Devices—A clock, stopwatch, digital timer, or alikesimilar readable to 1 minute.
D7012 − 23
7. Safety PrecautionsHazards
7.1 Danger exists near confining pressure testing equipment because of the high pressures and loads developed within the system.
Test systems mustshall be designed and constructed with adequate safety factors, assembled with properly rated fittings, fittings
rated for the pressure to be used, and provided with protective shields to protect people in the area from unexpected system failure.
The use of a gas as the confining pressure fluid introduces potential for extreme violence in the event of a system failure.
7.2 Many rock types fail in a violent manner when loaded to failure in compression. A protective shield shall be placed around
the uniaxial test specimen to prevent injury from flying rock fragments.
7.3 Elevated temperatures increase the risks of electrical shorts and fire. The flash point of the confining pressure fluid shall be
above the operating temperatures during the test.
8. Test Specimens
8.1 Specimen Selection—The specimens for each sample shall be selected from cores representing a valid average of the type of
rock under consideration. This sample selection can be achieved by visual observations of mineral constituents, grain sizes and
shape, partings and defects such as pores and fissures, or by other methods such as ultrasonic velocity measurements. The
minimum diameter of rock test specimens shall be at least ten times the diameter of the largest mineral grain. For weak rock types,
which behave more like soil, for example, weakly cemented sandstone, the minimum specimen diameter shall be at least six times
the maximum particle diameter. The specified minimum specimen diameter of approximately 47-mm 47 mm satisfy this criterion
in the majority of cases. When cores of diameter smaller than the specified minimum must be tested because of the unavailability
of larger diameter core, as is often the case in the mining industry, suitable notation of this fact shall be made in the report.
8.1.1 Desirable specimen length to diameter ratios are between 2.0:1 and 2.5:1. Specimen length to diameter ratios of less than
2.0:1 are unacceptable. If it is necessary to test specimens not meeting the length to diameter ratio requirements due to lack of
available specimens, the report shall contain a note stating the non-conformance with this standard including a statement explaining
that the results may differ from results obtained from a test specimen that meets the requirements. Laboratory specimen length to
diameter ratios must be employed with proper judgment in engineering applications.
8.1.2 The number of specimens necessary to obtain a specific level of statistical results may be determined using Test Method
E122. However, it may not be economically possiblepracticable to achieve a specific confidence level and professional judgment
may be necessary.
8.2 Preparation—Test specimens shall be prepared in accordance with Practice D4543.
8.2.1 Test results for specimens not meeting the requirements of Practice D4543 shall contain a note describing the
non-conformance and a statement explaining that the results reported may differ from results obtained from a test specimen that
meets the requirements of Practice D4543.
8.3 Moisture condition of the specimen at
...