1、Designation: D 5335 04Standard Test Method forLinear Coefficient of Thermal Expansion of Rock UsingBonded Electric Resistance Strain Gages1This standard is issued under the fixed designation D 5335; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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. Scope*1.1 This test method covers the laboratory determination ofthe linear (one-dimensional) coef
3、ficient of thermal expansionof rock using bonded electric resistance strain gages.1.2 This test method is applicable for unconfined pressureconditions over the temperature range from 20 to 260C (68 to500F).NOTE 1Unconfined tests performed at elevated temperatures mayalter the mineralogy or grain str
4、ucture of the test specimen. This alterationmay change the physical and thermal properties of the test specimen.NOTE 2The strain gages are mounted with epoxy. Most commerciallyavailable high temperature epoxies require elevated temperature curing.The elevated temperature required for this curing may
5、 alter the physicaland thermal properties of the test specimen. Epoxy should be selectedbased upon the maximum expected test temperature. Room temperaturecuring epoxy should be used whenever possible.1.3 The test specimens may be either saturated or dry. Ifsaturated specimens are used, then the test
6、 temperature shall beat least 10C (18F) less than the boiling point of the saturatingfluid in order to minimize the effects of evaporization of thefluid.NOTE 3When testing a saturated specimen, the moisture content ofthe specimen may change unless special precautions are taken to encap-sulate the te
7、st specimen. Refer to 7.4.1.4 For satisfactory results in conformance with this testmethod, the principles governing the size, construction, anduse of the apparatus described in this test method should befollowed. If the results are to be reported as having beenobtained by this test method, then all
8、 pertinent requirementsprescribed in this test method shall be met.1.5 It is not practicable in a test method of this type to aimto establish details of construction and procedure to cover allcontingencies that might offer difficulties to a person withouttechnical knowledge concerning the theory of
9、heat flow,temperature measurement, and general testing practices. Stan-dardization of this test method does not reduce the need forsuch technical knowledge. It is recognized also that it would beunwise, because of the standardization of this test method, toresist in any way the further development o
10、f improved or newmethods or procedures by research workers.1.6 The values stated in SI units are to be regarded as thestandard. The inch-pound units given in parentheses are forinformation only.1.7 All observed and calculated values shall conform to theguidelines for significant digits and rounding
11、established inPractice D 6026.1.7.1 The method used to specifiy how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond i
12、ts scope.1.8 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 requirements prior to use.2. Re
13、ferenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock and ContainedFluidsD 2113 Practice for Rock Core Drilling and Sampling ofRock for Site InvestigationD 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and RockD 3740 Practice for Minimum Re
14、quirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 6026 Practice for Using Significant Digits in Geotechni-cal DataE 83 Practice for Verification and Classification of Exten-sometersE 122 Practices for Choice of Sample Size
15、 to Estimate aMeasure of Quality for a Lot or ProcessE 228 Test Method for Linear Thermal Expansion of SolidMaterials With a Vitreous Silica Dilatometer1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mec
16、hanics.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 1992. Last previous edition approved in 1999 as D 5335 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan
17、dards volume information, refer to the standards Document Summary page onthe ASTM website.1*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.E 289 Test Method for Linear
18、Thermal Expansion of RigidSolids with Interferometry3. Terminology3.1 See Terminology D 653 for general definitions.3.2 Definitions of Terms Specific to This Standard:3.2.1 linear coeffcient of thermal expansionthe change inlength of a unit length for a temperature change of 1. Themathematical expre
19、ssion is:a 5 L22 L1!/L0# 3 1/T22 T1!# (1)In terms of thermal strains:a 5 eT22eT1!/T22 T1! 5DeT/DT (2)where eT1and eT2are the thermal strains of the specimen asa result of a temperature change from T0to T1and from T0toT2respectively, a is obtained by dividing the change in thermalstrain (DeT) by the
20、change in temperature (DT). The units of aare millimetres/millimetre per degree Celsius (inches/inch perdegree Fahrenheit).3.2.2 thermal strainthe change in length of a unit lengthof a sample due to a change in temperature. The mathematicalexpression is:eT5L22 L1L0(3)where L1and L2are the specimen l
21、engths at temperatures T1and T2, respectively, and L0is the specimen length at thereference temperature T0.4. Summary of Test Method4.1 The application of heat to rock causes it to expand. Thischange in dimension of the rock when divided by the length ofrock is the strain developed in the rock. A wi
22、re or foil gridsuitably bonded to the rock will be strained precisely the sameamount as the rock. This straining, or stretching, of the gridresults in a change in the electrical resistance of the grid.Measurement of the change in the electrical resistance of thegrid is thus a measure of the change i
23、n dimension of the rock.4.2 The application of heat to the grid may cause a changein the electrical resistance of the grid. To eliminate errors dueto gage heating, a second grid is attached to a referencespecimen and the output of the gage attached to the referencespecimen is subtracted from the out
24、put of the gage attached tothe test specimen.5. Significance and Use5.1 Information concerning the thermal expansion charac-teristics of rocks is important in the design of any undergroundexcavation where the temperature of the surrounding rock maybe altered. Thermal strain causes thermal stress tha
25、t ultimatelyaffects the stability of underground excavations. Examples ofapplications where rock thermal strain is important include:nuclear waste repositories, underground power stations, com-pressed air energy storage facilities, and geothermal energyfacilities.5.2 The linear coefficient of therma
26、l expansion, a, of rock isknown to vary as the temperature changes. Rock thermal strainis normally not a linear function of temperature. This testmethod provides a procedure for continuously monitoringthermal strain as a function of temperature. Therefore, infor-mation on how a changes with temperat
27、ure is obtained.5.3 Other methods of measuring the expansion coefficient ofrock by averaging the thermal strain of a large specimen overa temperature range of many degrees may result in failure todetermine the variation in a of that rock for one or more of thefollowing reasons:5.3.1 Alpha is not alw
28、ays linear with temperature,5.3.2 Some rocks are anisotropic having directional charac-teristics which can vary by more than a factor of two.5.3.3 Alpha may have a negative value in one direction and,at the same time, a positive value in the others.5.4 Strain gages, both wire and foil types, have be
29、ensuccessfully employed to measure the thermal expansioncoefficients of rock. These coefficients are frequently verysmall, being on the order of millionths of a millimetre permillimetre for each degree Celsius (millionths of an inch perinch for each degree Fahrenheit). The thermal strain of rocks is
30、about one tenth that of plastics and one half or one quarter thatof many metals. Therefore, measurement methods for rocksrequire greater precision than methods that are routinely usedon plastics and metals.NOTE 4Notwithstanding the statements on precision and bias con-tained in this test method; the
31、 precision of this test method is dependenton the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Users of this test method are ca
32、utioned that compliance withPractice D 3740 does not in itself assure reliable testing. Reliable testingdepends on many factors; Practice D 3740 provides a means of evaluatingsome of those factors.6. Apparatus6.1 Bonded Strain Gages, corresponding to ASTM Class Aresistance strain gage extensometer (
33、see Practice E83). Thegage length shall be at least ten times the largest grain in therock. Care shall be exercised to have the same length and typeof connecting wires on all specimens.6.2 Strain-Measuring System, having sensitivity of at least 5m/m (5 in./in.) with an accuracy of at least 60.1 % of
34、 thereading and a linearity of at least 60.1 % of the interval.6.3 Reference Specimen, having minimum dimensions atleast twice the length of the strain gage. The referencespecimen shall have a maximum linear coefficient of thermalexpansion of 0.5 3 106cm/cmC (0.9 3 106in./in.F).NOTE 5Suitable refere
35、nce materials include titanium silicate, Zero-dur, and ultra-low expansion glass, all having expansion coefficients ofless than 0.5 3 106/C (0.9 3 106/F) over the temperature range from 0to 200C (32 to 400F)6.4 Temperature Measurement SystemThe system chosento monitor and record temperature depends
36、primarily on thetest apparatus and the maximum test temperature. Speciallimits of error thermocouples or platinum resistance thermom-eters (RTDs) are recommended. The temperature sensor (trans-ducer) shall be accurate to better than 0.2C (0.5F) with aresolution of better than 0.05C (0.1F).6.5 Heatin
37、g SystemThe heating unit (furnace) shall belarge enough to contain the test calibration, and referencespecimens such that the gage length specified in 6.1 can beD5335042maintained at a constant temperature over its length to 0.1C(0.2F). It shall also incorporate controls so that specimensmay be heat
38、ed or cooled at a rate not greater than 1C(1.8F)/min while still maintaining the constant temperaturealong the gage length. If the heating unit consists of a liquidbath, then the specimens shall be encapsulated to preventpenetration of the fluid into the specimens.7. Sampling7.1 ScopeRock samples ca
39、n be in the form of blocksamples or core samples. The number and types of rocksamples needed depends partly on the intended application ofthe test results. For example, an initial mechanical character-ization of the site might require several samples from a varietyof formations, while a detailed the
40、rmomechanical investigationof a specific rock type may require many tests from a singleformation.The final testing program will depend heavily on thetechnical judgment and experience of project personnel. Addi-tional information may be found in Practice D 2113, whichdescribes rock core drilling and
41、sampling of rock for siteinvestigations.7.2 Statistical RequirementsThe number of samples andspecimens tested shall be sufficient to provide an adequatestatistical basis for evaluation of the results. Rock types that arehighly variable will require more tests than relatively uniformrocks in order to
42、 evaluate the results with equal uncertainty.7.2.1 The number of samples and specimens required toobtain a specific level of statistically valid results may bedetermined using test method E 122. However, it may not beeconomically possible to achieve specific confidence levels andprofessional judgmen
43、t may be required7.3 NonhomogenitiesDiscontinuities in the rock mass,such as joints, inclusions, voids, veins, bedding, etc., caninfluence the thermal expansion of the rock. Microcracks maybe produced during sampling or test preparation.7.4 Moisture Condition of SamplesThe moisture condi-tion of the
44、 rock can influence the measured thermal expansion.It is recommended that specimens be tested in both natural anddry conditions. For natural conditions, preserve the moisturecontent of the rock between the time of recovery and testing.7.5 AnisotropyThe thermal expansion coefficient of manyrocks is d
45、ependent on direction. Therefore, thermal expansionshould be measured in several directions in order to assess thedegree of anisotropy.7.6 DocumentationSince the thermal expansion of mostrocks is anisotropic, it is important that the field orientation ofeach sample is recorded. The orientation of ea
46、ch sample shallbe noted on the sample and suitable markings shall be carriedthrough each cutting to the final specimen ready for testing.These markings should indicate compass direction, up/downdirections, and orientation with respect to geologic structure.8. Test Specimens8.1 DimensionsTest specime
47、ns shall be right circularcylinders or right prisms. The minimum dimensions shall beadequate to accommodate the strain gages as specified in 6.1.8.2 Preparation:8.2.1 Use a segmented diamond saw for cutting core orblock samples into right circular cylinders or right prisms.Right circular cylinders a
48、re easily produced by cutting a coresample at two locations as required by 8.1, parallel to eachother and at right angles to the longitudinal axis.Apply coolingfluid continuously to cool the blade and flush cuttings from thecut. If required, laboratory core drilling of the rock blocksamples can be d
49、one to obtain drill cores.8.2.2 The areas on the specimen where the strain gages areto be mounted shall be smooth to within 0.025 mm (0.001 in.).8.2.3 Do not degrade the rock during the machining process.Prevent thermal fracturing by cooling with an appropriate fluidas required. Generally, water is used for hard rock, but somematerials require special fluids, such as saturated brine for saltor glycerin for expansive shales.8.3 DryingIf the specimen is to be tested dry, dry it at80C (176F) in a heating unit, as described in 6.5, for
