1、Designation: D 7012 07Standard Test Method forCompressive Strength and Elastic Moduli of Intact RockCore Specimens under Varying States of Stress andTemperatures1This standard is issued under the fixed designation D 7012; the number immediately following the designation indicates the year oforiginal
2、 adoption or, in the case of revision, the 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.1. Scope1.1 This test method covers the determination of thestrength of intact
3、 rock core specimens in uniaxial compressionand confined compression. The tests provide data in determin-ing the strength of rock, namely: the uniaxial strength, shearstrengths at varying pressures and varying temperatures, angleof internal friction, (angle of shearing resistance), and cohesioninter
4、cept. The test method specifies the apparatus, instrumen-tation, and procedures for determining the stress-axial strainand the stress-lateral strain curves, as well asYoungs modulus,E, and Poissons ratio, y. It should be observed that this methodmakes no provision for pore pressure measurements ands
5、pecimens are undrained (platens are not vented). Thus thestrength values determined are in terms of total stress, that is,are not corrected for pore pressures. This test method does notinclude the procedures necessary to obtain a stress-strain curvebeyond the ultimate strength.1.1.1 This standard re
6、places and combines the followingStandard Test Methods for: D 2664 Triaxial CompressiveStrength of Undrained Rock Core Specimens Without PorePressure Measurements; D 5407 Elastic Moduli of UndrainedRock Core Specimens in Triaxial Compression Without PorePressure Measurements; D 2938 Unconfined Compr
7、essiveStrength of Intact Rock Core Specimens; and D 3148 ElasticModuli of Intact Rock Core Specimens in Uniaxial Compres-sion.1.1.2 The original four standards are now referred to asMethods in this standard as follows: Method A TriaxialCompressive Strength of Undrained Rock Core SpecimensWithout Por
8、e Pressure Measurements; Method B ElasticModuli of Undrained Rock Core Specimens in Triaxial Com-pression Without Pore Pressure Measurements; Method C Unconfined Compressive Strength of Intact Rock Core Speci-mens; Method D Elastic Moduli of Intact Rock CoreSpecimens in Uniaxial Compression; and Opt
9、ionA ElevatedTemperatures.1.2 For an isotropic material, the relation between the shearand bulk moduli and Youngs modulus and Poissons ratio are:G 5E21 1y!(1)K 5E31 2 2y!(2)where:G = shear modulus,K = bulk modulus,E = Youngs modulus, andy = Poissons ratio.1.2.1 The engineering applicability of these
10、 equations de-creases with increasing anisotropy of the rock. It is desirable toconduct tests in the plane of foliation, cleavage or bedding andat right angles to it to determine the degree of anisotropy. It isnoted that equations developed for isotropic materials may giveonly approximate calculated
11、 results if the difference in elasticmoduli in two orthogonal directions is greater than 10 % for agiven stress level.NOTE 1Elastic moduli measured by sonic methods (Test MethodD 2845) may often be employed as preliminary measures of anisotropy.1.3 This test method given for determining the elasticc
12、onstants does not apply to rocks that undergo significantinelastic strains during the test, such as potash and salt. Theelastic moduli for such rocks should be determined fromunload-reload cycles, that are not covered by this test method.1.4 The values stated in SI units are to be regarded as thesta
13、ndard.1.5 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1This tes
14、t 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 July 1, 2007. Published July 2007. Originally approvedin 2004. Last previous edition approved in 2004 as D 701204e1.1Copyright AS
15、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2. Referenced Documents2.1 ASTM Standards:2D 2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD 2845 Test Method for Laboratory Determination of Pu
16、lseVelocities and Ultrasonic Elastic Constants of RockD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4543 Practices for Preparing Rock Core as CylindricalTest Specimens and Verifying Confor
17、mance to Dimen-sional and Shape TolerancesE4 Practices for Force Verification of Testing MachinesE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lot or Process2.2 ASTM Adjunct:3Triaxial Compression Chamber Drawings (3)3. S
18、ummary of Test Method3.1 A rock core specimen is cut to length and the ends aremachined flat. The specimen is placed in a loading frame andif required, placed in a loading chamber and subjected toconfining pressure. In an elevated temperature test the speci-men is heated to the desired test temperat
19、ure. Axial load isincreased continuously on the specimen, and deformation ismeasured as a function of load until peak load and failure areobtained.4. Significance and Use4.1 The parameters obtained from these procedures are interms of undrained total stress (as already mentioned in 1.1.1.).However,
20、there are some cases where either the rock type orthe loading condition of the problem under consideration willrequire the effective stress or drained parameters be deter-mined.4.2 Unconfined compressive strength of rock is used inmany design formulas and is sometimes used as an indexproperty to sel
21、ect the appropriate excavation technique. Defor-mation and strength of rock are known to be functions ofconfining pressure. The confined compression test is com-monly used to simulate the stress conditions under which mostunderground rock masses exist. The elastic constants are usedto calculate the
22、stress and deformation in rock structures.4.3 The deformation and strength properties of rock coresmeasured in the laboratory usually do not accurately reflectlarge-scale in situ properties because the latter are stronglyinfluenced by joints, faults, inhomogeneities, weakness planes,and other factor
23、s. Therefore, laboratory values for intactspecimens must be employed with proper judgment in engi-neering applications.NOTE 2Notwithstanding the statements on precision and bias con-tained in this test method; the measures of precision of these test methodsare dependent on the competence of the pers
24、onnel performing them, andon the suitability of the equipment and facilities used. Agencies that meetthe criteria of Practice D 3740 are generally considered capable ofcompetent and objective testing. Users of this test method are cautionedthat compliance with Practice D 3740 does not in itself assu
25、re reliabletesting. Reliable testing depends on many factors; Practice D 3740provides a means for evaluating some of those factors.5. Apparatus5.1 Loading DeviceThe loading device shall be of suffi-cient capacity to apply load at a rate conforming to therequirements specified in 9.6. It shall be ver
26、ified at suitabletime intervals in accordance with the procedures given inPractices E4and comply with the requirements prescribed inthe method. The loading device may be equipped with adisplacement transducer that can be used to advance theloading ram at a specified rate.NOTE 3If the load-measuring
27、device is located outside the confiningcompression apparatus, calibrations to determine the seal friction need tobe made to ensure the accuracy specified in Practices E4.5.2 Confining Apparatus3The confined pressure appara-tus shall consist of a chamber in which the test specimen maybe subjected to
28、a constant lateral fluid pressure and the requiredaxial load. The apparatus shall have safety valves, suitableentry ports for filling the chamber, and associated hoses, gages,and valves as needed.5.3 Flexible MembraneThis membrane encloses the rockspecimen and extends over the platens to prevent pen
29、etrationby the confining fluid.Asleeve of natural or synthetic rubber orplastic is satisfactory for room temperature tests; however,metal or high-temperature rubber (for example, viton) jacketsare usually required for elevated temperature tests. The mem-brane shall be inert relative to the confining
30、 fluid and shallcover small pores in the specimen without rupturing whenconfining pressure is applied. Plastic or silicone rubber coat-ings may be applied directly to the specimen provided thesematerials do not penetrate and strengthen or weaken thespecimen. Care must be taken to form an effective s
31、eal wherethe platen and specimen meet. Membranes formed by coatingsshall be subject to the same performance requirements aselastic sleeve membranes.5.4 Pressure-Maintaining DeviceA hydraulic pump, pres-sure intensifier, or other system shall have sufficient capacity tomaintain constant the desired l
32、ateral pressure. The pressuriza-tion system shall be capable of maintaining the confiningpressure constant to within 61 % throughout the test. Theconfining pressure shall be measured with a hydraulic pressuregage or electronic transducer having an accuracy of at least 61percent of the confining pres
33、sure, including errors due toreadout equipment, and a resolution of at least 0.5 % of theconfining pressure.5.5 Confining-Pressure FluidsFor room temperature tests,hydraulic fluids compatible with the pressure-maintainingdevice shall be used. For elevated temperature tests, the fluidmust remain stab
34、le at the temperature and pressure levelsdesignated for the test.5.6 Elevated-Temperature EnclosureThe elevated tem-perature enclosure shall be either an internal system that fits2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
35、 For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from: ASTM International Headquarters. Order Adjunct No.ADJD2664. Original adjunct produced in 1982.D7012072inside the loading apparatus or the confining pressure appara-t
36、us, an external system enclosing the entire confining pressureapparatus, or an external system encompassing the completetest apparatus. For high temperatures, a system of heaters,insulation, and temperature-measuring devices are normallyrequired to maintain the specified temperature. Temperatureshal
37、l be measured at three locations, with one sensor near thetop, one at midheight, and one near the bottom of the specimen.The “average” specimen temperature, based on the midheightsensor, shall be maintained to within 61C of the required testtemperature. The maximum temperature difference betweenthe
38、midheight sensor and either end sensor shall not exceed3C.NOTE 4An alternative to measuring the temperature at three locationsalong the specimen during the test is to determine the temperaturedistribution in a specimen that has temperature sensors located in drillholes at a minimum of six positions:
39、 along both the centerline andspecimen periphery at midheight and each end of the specimen. Thespecimen may originate from the same batch as the test specimens andconform to the same dimensional tolerances and to the same degree ofintactness. The temperature controller set point may be adjusted to o
40、btainsteady-state temperatures in the specimen that meet the temperaturerequirements at each test temperature (the centerline temperature atmidheight may be within 61C of the required test temperature, and allother specimen temperatures may not deviate from this temperature bymore than 3C). The rela
41、tionship between controller set point andspecimen temperature can be used to determine the specimen temperatureduring testing provided that the output of the temperature feedback sensor(or other fixed-location temperature sensor in the triaxial apparatus) ismaintained constant within 61C of the requ
42、ired test temperature. Therelationship between temperature controller set point and steady-statespecimen temperature may be verified periodically. The specimen is usedsolely to determine the temperature distribution in a specimen in thetriaxial apparatus. It is not to be used to determine compressiv
43、e strengthor elastic constants.5.7 Temperature Measuring DeviceSpecial limits-of-errorthermocouples or platinum resistance thermometers (RTDs)having accuracies of at least 6 1C with a resolution of 0.1Cshall be used.5.8 PlatensTwo steel platens are used to transmit the axialload to the ends of the s
44、pecimen. They shall be made oftool-hardened steel to a minimum Rockwell Hardness of 58 onthe “C” scale. One of the platens shall be spherically seated andthe other shall be a plain rigid platen. The bearing faces shallnot depart from a plane by more than 0.015 mm when theplatens are new and shall be
45、 maintained within a permissiblevariation of 0.025 mm. The diameter of the spherical seat shallbe at least as large as that of the test specimen, but shall notexceed twice the diameter of the test specimen. The center ofthe sphere in the spherical seat shall coincide with that of thebearing face of
46、the specimen. The spherical seat shall beproperly lubricated to assure free movement. The movableportion of the platen shall be held closely in the spherical seat,but the design shall be such that the bearing face can be rotatedand tilted through small angles in any direction. If a sphericalseat is
47、not used, the bearing faces of the blocks shall be parallelto 0.0005 mm/mm of platen diameter. The platen diametershall be at least as great as that of the specimen and have alength-to-diameter ratio of at least 1:2.5.9 Strain/Deformation Measuring DevicesThe strain/deformation measuring system shal
48、l measure the strain with aresolution of at least 25 3 10-6strain and an accuracy within2 % of the value of readings above 250 3 10-6strain andaccuracy and resolution within 5 3 10 -6 for readings lowerthan 250 3 10-6strain, including errors introduced by excita-tion and readout equipment. The syste
49、m shall be free fromnon-characterized long-term instability (drift) that results in anapparent strain of 10-8/s or greater.NOTE 5The user is cautioned about the influence of pressure andtemperature on the output of strain and deformation sensors located withinthe confining pressure apparatus.5.9.1 Determination of Axial StrainThe axial deforma-tions or strains may be determined from data obtained byelectrical resistance strain gages, compressometers, linear vari-able differential transformers (LVDTs), or other suitablemeans. The design of the measu
