ASTM D2664-95a
(Test Method)Standard Test Method for Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements
Standard Test Method for Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements
SCOPE
1.1 This test method covers the determination of the strength of cylindrical rock core specimens in an undrained state under triaxial compression loading. The test provides data useful in determining the strength and elastic properties of rock, namely: shear strengths at various lateral pressures, angle of internal friction, (angle of shearing resistance), cohesion intercept, and Young's modulus. It should be observed that this method makes no provision for pore pressure measurements. Thus the strength values determined are in terms of total stress, that is, not corrected for pore pressures.
1.2 The values stated in inch-pound units are to be regarded as the standard.
1.3 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.
General Information
Standards Content (Sample)
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Designation: D 2664 – 95a
Standard Test Method for
Triaxial Compressive Strength of Undrained Rock Core
Specimens Without Pore Pressure Measurements
This standard is issued under the fixed designation D 2664; 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 4. Apparatus
1.1 This test method covers the determination of the 4.1 Loading Device—A suitable device for applying and
strength of cylindrical rock core specimens in an undrained measuring axial load to the specimen. It shall be of sufficient
state under triaxial compression loading. The test provides data capacity to apply load at a rate conforming to the requirements
useful in determining the strength and elastic properties of specified in 7.2. It shall be verified at suitable time intervals in
rock, namely: shear strengths at various lateral pressures, angle accordance with the procedures given in Practices E 4 and
of internal friction, (angle of shearing resistance), cohesion comply with the requirements prescribed in the method.
intercept, and Young’s modulus. It should be observed that this 4.2 Pressure-Maintaining Device—A hydraulic pump, pres-
method makes no provision for pore pressure measurements. sure intensifier, or other system of sufficient capacity to
Thus the strength values determined are in terms of total stress, maintain constant the desired lateral pressure, s .
that is, not corrected for pore pressures.
NOTE 1—A pressure intensifier as described by Leonard Obert in U.S.
1.2 The values stated in inch-pound units are to be regarded
Bureau of Mines Report of Investigations No. 6332, “An Inexpensive
as the standard.
Triaxial Apparatus for Testing Mine Rock,” has been found to fulfill the
1.3 This standard does not purport to address all of the
above requirements.
safety concerns, if any, associated with its use. It is the 5
4.3 Triaxial Compression Chamber —An apparatus in
responsibility of the user of this standard to establish appro-
which the test specimen may be enclosed in an impermeable
priate safety and health practices and determine the applica-
flexible membrane; placed between two hundred platens, one
bility of regulatory limitations prior to use.
of which shall be spherically seated; subjected to a constant
lateral fluid pressure; and then loaded axially to failure. The
2. Referenced Documents
platens shall be made of tool steel hardened to a minimum of
2.1 ASTM Standards:
Rockwell 58 HRC, the bearing faces of which shall not depart
D 4543 Practice for Preparing Rock Core Specimens and
from plane surfaces by more than 0.0005 in. (0.0127 mm)
Determining Dimensional and Shape Tolerances
when the platens are new and which shall be maintained within
E 4 Practices for Force Verification of Testing Machines
a permissible variation of 0.001 in. (0.025 mm). In addition to
E 122 Practice for Choice of Sample Size to Estimate a
the platens and membrane, the apparatus shall consist of a
Measure of Quality for a Lot or Process
high-pressure cylinder with overflow valve, a base, suitable
entry ports for filling the cylinder with hydraulic fluid and
3. Significance and Use
applying the lateral pressure, and hoses, gages, and valves as
3.1 Rock is known to behave as a function of the confining
needed.
pressure. The triaxial compression test is commonly used to
4.4 Deformation and Strain-Measuring Devices—High-
simulate the stress conditions under which most underground
grade dial micrometers or other measuring devices graduated
rock masses exist.
to read in 0.0001-in. (0.0025-mm) units, and accurate within
0.0001 in. (0.0025 mm) in any 0.0010-in. (0.025-mm) range,
and within 0.0002 in. (0.005 mm) in any 0.0100-in. (0.25-mm)
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
range shall be provided for measuring axial deformation due to
and Rock and is the direct responsibility of Subcommittee D18.12 on Rock
Mechanics.
Current edition approved Dec. 10, 1995. Published April 1996. Originally
published as D 2664 – 67. Last previous edition D 2664 – 86 (1995). Assembly and detail drawings of an apparatus that meets these requirements
Annual Book of ASTM Standards, Vol 04.08. and which is designed to accommodate 2 ⁄8-in. (53.975-mm) diameter specimens
Annual Book of ASTM Standards, Vols 03.01, 14.02. and operate at a lateral fluid pressure of 10 000 psi (689 MPa) are available from
Annual Book of ASTM Standards, Vol 14.02. Headquarters. Request Adjunct No. 12-426640-00.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 2664 – 95a
loading. These may consist of micrometer screws, dial mi- apply sufficient axial load to prevent the deformation measur-
crometers, or linear variable differential transformers securely ing device from deviating from the initial reading. When the
attached to the high pressure cylinder. predetermined test level of fluid pressure is reached, note and
4.4.1 Electrical resistance strain gages applied directly to record the axial load registered by the loading device. Consider
the rock specimen in the axial direction may also be used. In this load to be the zero or starting load for the test.
addition, the use of circumferentially applied strain gages will 7.2 Apply the axial load continuously and without shock
permit the observation of data necessary in the calculation of until the load becomes constant, or reduces, or a predetermined
Poisson’s ratio. In this case two axial (vertical) gages should be amount of strain is achieved. Apply the load in such a manner
mounted on opposite sides of the specimen at mid-height and as to produce a strain rate as constant as feasible throughout the
two circumferential (horizontal) gages similarly located around test. Do not permit the strain rate at any given time to deviate
the circumference, but in the direction perpendicular to the by more than 10 % from that selected. The strain rate selected
axial gages. should be that which will produce failure of a similar test
4.5 Flexible Membrane—A flexible membrane of suitable specimen in unconfined compression, in a test time of between
material to exclude the confining fluid from the specimen, and 2 and 15 min. The selected strain rate for a given rock type
that shall not significantly extrude into abrupt surface pores. It shall be adhered to for all tests in a given series of investigation
should be sufficiently long to extend well onto the platens and (Note 3). Maintain constant the predetermined confining pres-
when slightly stretched be of the same diameter as the rock sure throughout the test and observe and record readings of
specimen. deformation as required.
NOTE 2—Neoprene rubber tubing of ⁄16-in. (1.588-mm) wall thickness NOTE 3—Results of tests by other investigators have shown that strain
and of 40 to 60 Durometer hardness, Shore Type A or various sizes of rates within this range will provide strength values that are reasonably free
bicycle inner tubing, have been found generally suitable for this purpose. from rapid loading effects and reproducible within acceptable tolerances.
7.3 To make sure that no testing fluid has penetrated into the
5. Sampling
specimen, the specimen membrane shall be carefully checked
5.1 The specimen shall be selected from the cores to
for fissures or punctures at the completion of each triaxial test.
represent a true average of the type of rock under consider-
If in question, weigh the specimen before and after the test.
ation. This can be achieved by visual observations of mineral
constituents, grain sizes and shapes, partings and defects such
8. Calculation
as pores and fissures.
8.1 Make the following calculations and graphical plots:
8.1.1 Construct a stress difference versus axial strain curve
6. Test Specimens
(Note 5). Stress difference is defined as the maximum principal
6.1 Preparation—The test specimens shall be prepared in
axial stress,s , minus the lateral pressure, s . Indicate the
1 3
accordance with Practice D 4543.
value of the lateral pressure, s , on the curve.
6.2 Moisture condi
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