ASTM D2936-95(2001)
(Test Method)Standard Test Method for Direct Tensile Strength of Intact Rock Core Specimens
Standard Test Method for Direct Tensile Strength of Intact Rock Core Specimens
SCOPE
1.1 This test method covers the determination of the direct tensile strength of intact cylindrical rock specimens.
1.2 The values stated in SI units are to be regarded as 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
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Standards Content (Sample)
Designation: D 2936 – 95 (Reapproved 2001)
Standard Test Method for
Direct Tensile Strength of Intact Rock Core Specimens
This standard is issued under the fixed designation D 2936; 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 conforming to the requirements of 8.2. The device shall be
verified at suitable time intervals in accordance with the
1.1 This test method covers the determination of the direct
procedures given in Practices E 4 and shall comply with the
tensile strength of intact cylindrical rock specimens.
requirements prescribed therein.
1.2 The values stated in SI units are to be regarded as
5.2 Caps—Cylindrical metal caps that, when cemented to
standard.
the specimen ends, provide a means through which the direct
1.3 This standard does not purport to address all of the
tensile load can be applied. The diameter of the metal caps
safety concerns, if any, associated with its use. It is the
shall not be less than that of the test specimen, nor shall it
responsibility of the user of this standard to establish appro-
exceed the test specimen diameter by more than 1.10 times.
priate safety and health practices and determine the applica-
Caps shall have a thickness of at least 30 mm (1 ⁄4 in.). Caps
bility of regulatory limitations prior to use.
shall be provided with a suitable linkage system for load
2. Referenced Documents
transfer from the loading device to the test specimen. The
linkage system shall be so designed that the load will be
2.1 ASTM Standards:
transmitted through the axis of the test specimen without the
D 2216 Test Method for Laboratory Determination of Water
application of bending or torsional stresses. The length of the
(Moisture) Content of Soil and Rock by Mass
linkages at each end shall be at least two times the diameter of
D 4543 Practice for Preparing f Rock Core Specimens and
the metal end caps. One such system is shown in Fig. 1.
Determining Dimensional and Shape Tolerances
E 4 Practices for Force Verification of Testing Machines
NOTE 1—Roller of link chain of suitable capacity has been found to
E 122 Practice for Calculating Sample Size to Estimate,
perform quite well in this application. Because roller chain flexes in one
With a Specified Tolerable Error, the Average for Charac- plane only, the upper and lower segments should be positioned at right
angles to each other to effectively reduce bending in the specimen.
teristic of a Lot or Process
Ball-and-socket, cable, or similar arrangements have been found to be
generally unsuitable as their tendency for bending and twisting makes the
3. Summary of Test Method
assembly unable to transmit a purely direct tensile stress to the test
3.1 A rock core sample is cut to length and its ends are
specimen.
cemented to metal caps. The metal caps are attached to a
testing machine and the specimen is loaded in tension until it 6. Sampling
fails.
6.1 Select the specimen from the cores to represent a valid
average of the type of rock under consideration. This can be
4. Significance and Use
achieved by visual observations of mineral constituents, grain
4.1 Rock is much weaker in tension than in compression.
sizes and shape, partings, and defects such as pores and
Thus, in determining the failure condition for a rock structure,
fissures, or by other methods such as ultrasonic velocity
many investigators employ tensile strength of the component
measurements.
rock as the failure strength for the structure. Direct tensile
stressing of rock is the most basic test for determining the 7. Test Specimens
tensile strength of rock.
7.1 Preparation—Prepare test specimens in accordance
with Practice D 4543, except that the degree of flatness and
5. Apparatus
smoothness of the specimen ends is not critical. End surfaces,
5.1 Loading Device, to apply and measure axial load on the
such as result from sawing with a diamond cutoff wheel, are
specimen, of sufficient capacity to apply the load at a rate
entirely adequate. Grinding, lapping, or polishing beyond this
point serves no useful purpose, and in fact, may adversely
This test method is under the jurisdiction of ASTM Committee D18 on Soil and
affect the adhesion of the cementing medium.
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
7.2 Water content of the specimen at the time of test can
Current edition approved June 15, 1995. Published August 1995. Originally
e2
have a significant effect upon the deformation of the rock.
published as D 2936 – 71. Last previous edition D 2936 – 84 (1989) .
Annual Book of ASTM Standards, Vol 04.08.
Good practice generally dictates that laboratory tests be made
Annual Book of ASTM Standards, Vols 03.01, 04.02, and 08.03.
upon specimens representative of field conditions. Thus, it
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2936
follows that the field water content of the specimen should be 10. Report
preserved until the time of test. On the other hand, there may
10.1 Report the following information:
be reasons for testing specimens at other water contents,
10.1.1 Source of sample including project name and loca-
including zero. In any case, the water content of the test
tion, and if known, storage environment (often location is
specimen should be tailored to the problem at hand and
frequently specified in terms of the borehole number and depth
reported in accordance with 10.1.6. If the water content of the
of specimen from the collar of the hole),
specimen is to be determined,
...
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