1、Designation: D 2936 95 (Reapproved 2004)e1Standard Test Method forDirect Tensile Strength of Intact Rock Core Specimens1This standard is issued under the fixed designation D 2936; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial corrections were made to this standard in November 2004.1. Scope1.1 This test method covers the determin
3、ation of the directtensile strength of intact cylindrical rock specimens.1.2 The values stated in SI units are to be regarded asstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to e
4、stablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD 4543 Practice for Preparing Rock C
5、ore Specimens andDetermining Dimensional and Shape TolerancesE 4 Practices for Force Verification of Testing MachinesE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for Charac-teristic of a Lot or Process3. Summary of Test Method3.1 A rock core sa
6、mple is cut to length and its ends arecemented to metal caps. The metal caps are attached to atesting machine and the specimen is loaded in tension until itfails.4. Significance and Use4.1 Rock is much weaker in tension than in compression.Thus, in determining the failure condition for a rock struct
7、ure,many investigators employ tensile strength of the componentrock as the failure strength for the structure. Direct tensilestressing of rock is the most basic test for determining thetensile strength of rock.5. Apparatus5.1 Loading Device, to apply and measure axial load on thespecimen, of suffici
8、ent capacity to apply the load at a rateconforming to the requirements of 8.2. The device shall beverified at suitable time intervals in accordance with theprocedures given in Practices E4and shall comply with therequirements prescribed therein.5.2 CapsCylindrical metal caps that, when cemented toth
9、e specimen ends, provide a means through which the directtensile load can be applied. The diameter of the metal capsshall not be less than that of the test specimen, nor shall itexceed the test specimen diameter by more than 1.10 times.Caps shall have a thickness of at least 30 mm (114 in.). Capssha
10、ll be provided with a suitable linkage system for loadtransfer from the loading device to the test specimen. Thelinkage system shall be so designed that the load will betransmitted through the axis of the test specimen without theapplication of bending or torsional stresses. The length of thelinkage
11、s at each end shall be at least two times the diameter ofthe metal end caps. .NOTE 1Roller of link chain of suitable capacity has been found toperform quite well in this application. Because roller chain flexes in oneplane only, the upper and lower segments should be positioned at rightangles to eac
12、h other to effectively reduce bending in the specimen.Ball-and-socket, cable, or similar arrangements have been found to begenerally unsuitable as their tendency for bending and twisting makes theassembly unable to transmit a purely direct tensile stress to the testspecimen.6. Sampling6.1 Select the
13、 specimen from the cores to represent a validaverage of the type of rock under consideration. This can beachieved by visual observations of mineral constituents, grainsizes and shape, partings, and defects such as pores andfissures, or by other methods such as ultrasonic velocitymeasurements.1This t
14、est method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved June 15, 1995. Published August 1995. Originallyapproved in 1971. Last previous edition approved in 2001 as D 2936 84 (2001).2F
15、or referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959, United States.7. Test Specimens7.1 PreparationPrepare test specimens in accordancewith Practice D 4543, except that the degree of flatness andsmoothness of the specimen ends is not critical. End surfaces,such as result from sawing with a diamond cutoff wheel, ar
17、eentirely adequate. Grinding, lapping, or polishing beyond thispoint serves no useful purpose, and in fact, may adverselyaffect the adhesion of the cementing medium.7.2 Water content of the specimen at the time of test canhave a significant effect upon the deformation of the rock.Good practice gener
18、ally dictates that laboratory tests be madeupon specimens representative of field conditions. Thus, itfollows that the field water content of the specimen should bepreserved until the time of test. On the other hand, there maybe reasons for testing specimens at other water contents,including zero. I
19、n any case, the water content of the testspecimen should be tailored to the problem at hand andreported in accordance with 10.1.6. If the water content of thespecimen is to be determined, follow the procedures given inTest Method D 2216.7.3 If water content is to be maintained, and the elevatedtempe
20、rature enclosure is not equipped with humidity control,seal the specimen using a flexible membrane or apply a plasticor silicone rubber coating to the specimen sides.8. Procedure8.1 Cement the metal caps to the test specimen to ensurealignment of the cap axes with the longitudinal axis of thespecime
21、n (see Note 2). The thickness of the cement layershould not exceed 1.5 mm (116 in.) at each end. The cementlayer must be of uniform thickness to ensure parallelismbetween the top surfaces of the metal caps attached to bothends of the specimens. This should be checked before thecement is hardened (se
22、e Note 1) by measuring the length of theend-cap assembly at three locations 120 apart and near theedge. The maximum difference between these measurementsshould be less than 0.10 mm (0.005 in.) for each 25.0 mm (1.0in.) of specimen diameter. After the cement has hardenedsufficiently to exceed the ten
23、sile strength of the rock, place thespecimen in the testing machine, making certain that the loadtransfer system is properly aligned.NOTE 2In cementing the metal caps to the test specimens, use jugsand fixtures of suitable design to hold the caps and specimens in properalignment until the cement has
24、 hardened. The chucking arrangement of amachine lathe or drill press is also suitable. Epoxy resin formulations ofrather stiff consistency and similar to those used as a patching and fillingcompound in automobile body repair work have been found to be asuitable cementing medium.8.2 Apply the tensile
25、 load continuously and without shockto failure. Apply the load or deformation at an approximatelyconstant rate such that failure will occur in not less than fivenor more than 15 min. Note and record the maximum loadcarried by the specimen during the test.NOTE 3In this test arrangement failure often
26、occurs near one of thecapped ends. Discard the results for those tests in which failure occurseither partly or wholly within the cementing medium.9. Calculation9.1 Calculate the tensile strength of the rock by dividing themaximum load carried by the specimen during the test by thecross-sectional are
27、a; express the result to the nearest 35.0 kPa(5 psi).10. Report10.1 Report the following information:10.1.1 Source of sample including project name and loca-tion, and if known, storage environment (often location isfrequently specified in terms of the borehole number and depthof specimen from the co
28、llar of the hole),10.1.2 Physical description of the sample including: rocktype, location and orientation of apparent planes, beddingplanes, and schistosity; and large inclusions or inhomogene-ities, if any,10.1.3 Date of sampling and testing,10.1.4 Specimen length and diameter, also conformancewith
29、 dimensional requirements,10.1.5 Rate of loading or deformation rate,10.1.6 General indication of water condition of sample attime of test, such as, as-received, saturated, laboratory air dry,or oven dry (it is recommended that the moisture condition bemore precisely determined when possible and rep
30、orted aseither water content or degree of saturation,10.1.7 Direct tensile strength for each specimen as calcu-lated, average direct tensile strength of all specimens, standarddeviation, or coefficient of variation,10.1.8 Type and location of failure (a sketch of the fracturedspecimen is recommended
31、), and10.1.9 Other available physical data.NOTE 4The number of specimens tested may depend upon theavailability of specimens, but normally a minimum of ten is preferred. Thenumber of specimens tested should be indicated. The statistical basis forrelating the number of specimens to the variability of
32、 measurements isgiven in Practice E 122.11. Precision and Bias11.1 PrecisionDue to the nature of the rock materialstested by this test method, it is, at this time, either not feasibleor too costly at this time to produce multiple specimens whichhave uniform mechanical properties. Therefore, since sp
33、eci-mens which would yield the same test results cannot be tested,Subcommittee D18.12 cannot determine the variation betweentests since any variation observed is just as likely to be due tospecimen variation as to operator or laboratory testing varia-tion. Subcommittee D18.12 welcomes proposals to r
34、esolve thisproblem that would allow for development of a valid precisionstatement.11.2 BiasThere is no accepted reference value for this testmethod; therefore, bias cannot be determined.12. Keywords12.1 loading tests; rock; tension (tensile) properties/tests;tensile strengthD 2936 95 (2004)e12ASTM I
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38、Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 2936 95 (2004)e13
