ASTM D3967-95a(2001)
(Test Method)Standard Test Method for Splitting Tensile Strength of Intact Rock Core Specimens
Standard Test Method for Splitting Tensile Strength of Intact Rock Core Specimens
SCOPE
1.1 This test method covers testing apparatus, specimen preparation, and testing procedures for determining the splitting tensile strength of rock by diametral line compression of a disk.
Note 1—The tensile strength of rock determined by tests other than the straight pull test is designated as the "indirect" tensile strength and, specifically, the value obtained in Section 8 of this test is termed the "splitting" tensile strength.
1.2 The values stated in SI 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.
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Designation:D3967–95a (Reapproved 2001)
Standard Test Method for
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Splitting Tensile Strength of Intact Rock Core Specimens
This standard is issued under the fixed designation D 3967; 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 also needed to insure positively that the disk specimens break
diametrally due to tensile pulling along the loading diameter.
1.1 This test method covers testing apparatus, specimen
preparation, and testing procedures for determining the split-
4. Apparatus
ting tensile strength of rock by diametral line compression of a
4.1 Loading Device, to apply and measure axial load on the
disk.
specimen, of sufficient capacity to apply the load at a rate
NOTE 1—The tensile strength of rock determined by tests other than the
conforming to the requirements in 7.3. It shall be verified at
straight pull test is designated as the “indirect” tensile strength and,
suitable time intervals in accordance with Practices E 4 and
specifically, the value obtained in Section 8 of this test is termed the
shall comply with the requirements prescribed therein.
“splitting” tensile strength.
4.2 Bearing Surfaces—The testing machine shall be
1.2 The values stated in SI units are to be regarded as the
equipped with two steel bearing blocks having a Rockwell
standard.
hardness of not less than 58 HRC (see Note 2).
1.3 This standard does not purport to address all of the
NOTE 2—False platens, with bearing faces conforming to the require-
safety concerns, if any, associated with its use. It is the
ments of this standard, may be used. These shall be oil hardened to more
responsibility of the user of this standard to establish appro-
than 58 HRC, and surface ground. With abrasive rocks these platens tend
priate safety and health practices and determine the applica-
to roughen after a number of specimens have been tested, and hence need
bility of regulatory limitations prior to use.
to be surfaced from time to time.
4.2.1 Flat Bearing Blocks—During testing the specimen
2. Referenced Documents
can be placed in direct contact with the machine bearing plates
2.1 ASTM Standards:
(or false platens, if used) (see Fig. 1). The bearing faces shall
2
E 4 Practices for Force Verification of Testing Machines
not depart from a plane by more than 0.0125 mm when the
E 691–92 Practice for Conducting an Interlaboratory Study
platens are new and shall be maintained within a permissible
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to Determine the Precision of a Test Method
variation of 0.025 mm. The bearing block diameter shall be at
least as great as the specimen thickness.
3. Significance and Use
4.2.2 Curved Bearing Blocks, may be used to reduce the
3.1 By definition the tensile strength is obtained by the
contact stresses. The radius of curvature of the supplementary
direct uniaxial tensile test. But the tensile test is difficult and
bearingplatesshallbesodesignedthattheirarcofcontactwith
expensive for routine application. The splitting tensile test
the specimen will in no case exceed 15° or that the width of
appears to offer a desirable alternative, because it is much
contact is less than D/6, where D is the diameter of the
simpler and inexpensive. Furthermore, engineers involved in
specimen.
rock mechanics design usually deal with complicated stress
fields, including various combinations of compressive and
NOTE 3—Since the equation used in 8.1 for splitting tensile strength is
derived based on a line load, the applied load shall be confined to a very
tensile stress fields. Under such conditions, the tensile strength
narrow strip if the splitting tensile strength test is to be valid. But a line
shouldbeobtainedwiththepresenceofcompressivestressesto
load creates extremely high contact stresses which cause premature
be representative of the field conditions. The splitting tensile
cracking. A wider contact strip can reduce the problems significantly.
strength test is one of the simplest tests in which such stress
Investigationsshowthatanarcofcontactsmallerthan15°causesnomore
fields occur. Since it is widely used in practice, a uniform test
than 2 % of error in principal tensile stress while reducing the incidence
method is needed for data to be comparable. A uniform test is
of premature cracking greatly.
4.2.3 Spherical Seating—One of the bearing surfaces
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should be spherically seated and the other a plain rigid block.
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics. The diameter of the spherical seat shall be at least as large as
Current edition approved Dec. 10, 1995. Pu
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