ASTM D3967-95a

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.

General Information

• Status: Historical
• Publication Date: 09-Dec-1995
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.12 - Rock Mechanics

Relations

• Replaced By: ASTM D3967-95a(2001) - Standard Test Method for Splitting Tensile Strength of Intact Rock Core Specimens
• Effective Date: 10-Dec-1995
• Referred By: ASTM D4992-22 - Standard Practice for Evaluation of Rock to be Used for Erosion Control
• Effective Date: 10-Dec-1995

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3967 – 95a
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
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 diametrally due to tensile pulling along the loading diameter.
1.1 This test method covers testing apparatus, specimen
4. Apparatus
preparation, and testing procedures for determining the split-
4.1 Loading Device, to apply and measure axial load on the
ting tensile strength of rock by diametral line compression of a
specimen, of sufficient capacity to apply the load at a rate
disk.
conforming to the requirements in 7.3. It shall be verified at
NOTE 1—The tensile strength of rock determined by tests other than the
suitable time intervals in accordance with Practices E 4 and
straight pull test is designated as the “indirect” tensile strength and,
shall comply with the requirements prescribed therein.
specifically, the value obtained in Section 8 of this test is termed the
4.2 Bearing Surfaces—The testing machine shall be
“splitting” tensile strength.
equipped with two steel bearing blocks having a Rockwell
1.2 The values stated in SI units are to be regarded as the
hardness of not less than 58 HRC (see Note 2).
standard.
NOTE 2—False platens, with bearing faces conforming to the require-
1.3 This standard does not purport to address all of the
ments of this standard, may be used. These shall be oil hardened to more
safety concerns, if any, associated with its use. It is the
than 58 HRC, and surface ground. With abrasive rocks these platens tend
responsibility of the user of this standard to establish appro-
to roughen after a number of specimens have been tested, and hence need
priate safety and health practices and determine the applica-
to be surfaced from time to time.
bility of regulatory limitations prior to use.
4.2.1 Flat Bearing Blocks—During testing the specimen
can be placed in direct contact with the machine bearing plates
2. Referenced Documents
(or false platens, if used) (see Fig. 1). The bearing faces shall
2.1 ASTM Standards:
not depart from a plane by more than 0.0125 mm when the
E 4 Practices for Load Verification of Testing Machines
platens are new and shall be maintained within a permissible
E 691–92 Practice for Conducting an Interlaboratory Study
variation of 0.025 mm. The bearing block diameter shall be at
to Determine the Precision of a Test Method
least as great as the specimen thickness.
4.2.2 Curved Bearing Blocks, may be used to reduce the
3. Significance and Use
contact stresses. The radius of curvature of the supplementary
3.1 By definition the tensile strength is obtained by the
bearing plates shall be so designed that their arc of contact with
direct uniaxial tensile test. But the tensile test is difficult and
the specimen will in no case exceed 15° or that the width of
expensive for routine application. The splitting tensile test
contact is less than D/6, where D is the diameter of the
appears to offer a desirable alternative, because it is much
specimen.
simpler and inexpensive. Furthermore, engineers involved in
rock mechanics design usually deal with complicated stress
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
fields, including various combinations of compressive and
narrow strip if the splitting tensile strength test is to be valid. But a line
tensile stress fields. Under such conditions, the tensile strength
load creates extremely high contact stresses which cause premature
should be obtained with the presence of compressive stresses to
cracking. A wider contact strip can reduce the problems significantly.
be representative of the field conditions. The splitting tensile
Investigations show that an arc of contact smaller than 15° causes no more
strength test is one of the simplest tests in which such stress
than 2 % of error in principal tensile stress while reducing the incidence
fields occur. Since it is widely used in practice, a uniform test
of premature cracking greatly.
method is needed for data to be comparable. A uniform test is
4.2.3 Spherical Seating—One of the bearing surfaces
also needed to insure positively that the disk specimens break
should be spherically seated and the other a plain rigid block.
The diameter of the spherical seat shall be at least as large as
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
that of the test specimen, but shall not exceed twice the
and Rock and is the direct responsibility of Subcommittee D18.12 on Rock
diameter of the test specimen. The center of the sphere in the
Mechanics.
spherical seat shall coincide with the center of the loaded side
Current edition approved Dec. 10, 1995. Published April 1996. Originally
published as D 3967 – 81. Last previous edition D 3967 – 95.
of the specimen. The spherical seat shall be lubricated to assure
Annual Book of ASTM Standards, Vol 03.01.
free movement. The movable portion of the platen shall be held
Annual Book of ASTM Standards, Vol 14.02.
D 3967
with a thickness-to-diameter ratio (t/D) between 0.2 and 0.75.
The diameter of the specimen shall be at least 10 times greater
than the largest mineral grain constituent. A diameter of 50 mm
(1 ⁄16 in.) (NX wireline core) will generally satisfy this
criterion.
NOTE 5—When cores smaller than the specified minimum must be
tested because of the unavailability of material, notation of the fact shall
be made in the test report.
NOTE 6—If the specimen shows apparent anisotropic features such as
bedding or schistosity, care shall be exercised in preparing the specimen
so that the orientation of the loading diameter relative to anisotropic
features can be determined precisely.
6.2 Number of specimens—At least ten specimens shall be
tested to obtain a meaningful average value. If the reproduc-
ibility of the test results is good (coefficient of variation less
than 5 %), a smaller number of specimens is acceptable.
6.3 The circumferential surface of the specimen shall be
smooth and straight to 0.50 mm (0.020 in.).
6.4 Cut the ends of the specimen parallel to each other and
at right angles to the longitudinal axis. The ends of the
specimen shall not deviate from perpendicular to the core axis
by more than 0.5°. This requirement can be generally met by
cutting the specimen with a precision diamond saw.
6.5 Determine the diameter of the specimen to the nearest
0.25 mm (0.01 in.) by taking the average of at least three
measurements, one of which shall be along the loading
diameter.
6.6 Determine the thickness of the specimen to the nearest
0.25 mm (0.01 in.) by taking the average of at least three
measurements, one of which shall be at the center of the disk.
FIG. 1 One of the Proposed Testing Setup for Splitting Tensile
6.7 The moisture conditions of the specimen at the time of
Str
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