Standard Test Method for Direct Tensile Strength of Intact Rock Core Specimens

SIGNIFICANCE AND USE
5.1 Rock is much weaker in tension than in compression. Thus, in determining the failure condition for a rock structure, many investigators employ the tensile strength of the component rock as the failure strength for the structure. Direct tensile stressing of rock is the most basic test for determining the tensile strength of rock. However, direct tensile tests will typically break at the weakest link along the longitudinal axis of the specimen, whether it is the rock substance or any discontinuity that is weaker than the adjacent rock substance. Unless the purpose of the direct tension tests is to get the strength across discontinuities the test results are on the conservative side and are more representative of the tensile strength at the rock substance scale. See Note 2 for additional significance and use information.
Note 2: The quality of the result produced by these practices is dependent upon 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 and sampling. Users of these practices are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers the determination of the direct tensile strength of the rock substance or discontinuities normal to the longitudinal axis of intact, isotropic cylindrical rock specimens at room temperature.  
1.2 Non-isotropic or even transversely isotropic specimens are not covered by this standard.  
1.3 Cylindrical rock specimens can be drill core from the field or rock blocks transported to the laboratory and drill core specimen obtained there.  
1.4 Specimen shapes other than cylindrical specimens, such as dog bone-shaped, are not covered by this standard.  
1.5 Test specimens may be tested under constant load or deformation rate.  
1.6 The values stated in SI units are to be regarded as standard. The values provided in parenthesis are for information only.  
1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 unless superseded by this standard.  
1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.9 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.

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Published
Publication Date
31-Dec-2019
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Drafting Committee
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ASTM D2936-20 - Standard Test Method for Direct Tensile Strength of Intact Rock Core Specimens
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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: D2936 − 20
Standard Test Method for
1
Direct Tensile Strength of Intact Rock Core Specimens
This standard is issued under the fixed designation D2936; 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* 2. Referenced Documents
2
1.1 This test method covers the determination of the direct
2.1 ASTM Standards:
tensile strength of the rock substance or discontinuities normal
D653 Terminology Relating to Soil, Rock, and Contained
to the longitudinal axis of intact, isotropic cylindrical rock
Fluids
specimens at room temperature.
D2113 Practice for Rock Core Drilling and Sampling of
Rock for Site Exploration
1.2 Non-isotropic or even transversely isotropic specimens
D2216 Test Methods for Laboratory Determination of Water
are not covered by this standard.
(Moisture) Content of Soil and Rock by Mass
1.3 Cylindrical rock specimens can be drill core from the
D2845 Test Method for Laboratory Determination of Pulse
field or rock blocks transported to the laboratory and drill core
Velocities and Ultrasonic Elastic Constants of Rock
specimen obtained there.
3
(Withdrawn 2017)
1.4 Specimen shapes other than cylindrical specimens, such
D3740 Practice for Minimum Requirements for Agencies
as dog bone-shaped, are not covered by this standard.
Engaged in Testing and/or Inspection of Soil and Rock as
Used in Engineering Design and Construction
1.5 Test specimens may be tested under constant load or
D4543 PracticesforPreparingRockCoreasCylindricalTest
deformation rate.
Specimens and Verifying Conformance to Dimensional
1.6 The values stated in SI units are to be regarded as
and Shape Tolerances
standard. The values provided in parenthesis are for informa-
D5079 Practices for Preserving and Transporting Rock Core
tion only.
3
Samples (Withdrawn 2017)
1.7 All observed and calculated values shall conform to the
D6026 Practice for Using Significant Digits in Geotechnical
guidelines for significant digits and rounding established in
Data
Practice D6026 unless superseded by this standard.
E4 Practices for Force Verification of Testing Machines
E122 Practice for Calculating Sample Size to Estimate,With
1.8 This standard does not purport to address all of the
Specified Precision, the Average for a Characteristic of a
safety concerns, if any, associated with its use. It is the
Lot or Process
responsibility of the user of this standard to establish appro-
E2586 Practice for Calculating and Using Basic Statistics
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Terminology
1.9 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1 Definitions:
ization established in the Decision on Principles for the
3.1.1 For definitions of common technical terms used in this
Development of International Standards, Guides and Recom-
standard, refer to Terminology D653.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 3.2 Definitions of Terms Specific to This Standard:
1 2
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Jan. 1, 2020. Published March 2020. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 1971. Last previous edition approved in 2008 as D2936 – 08, which the ASTM website.
3
was withdrawn January 2017 and reinstated in January 2020. DOI: 10.1520/D2936- The last approved version of this historical standard is referenced on
20. www.astm.org.
*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
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D2936 − 20
3.2.1 transverse isotropy, n—impliesthat,atanypointinthe stress concentrations were reduced by directly cementing end
rock, there is an axis of symmetry of rotation and that the rock caps of the same diameter to the specimen ends which results
has isotropic properties in a plane normal to this axis. in a similar stress distribution as in a uniaxial compression test.
6.2 If the specimen
...

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