ASTM_D_4612_-_16.pdf

Designation:D461216Standard Test Method forCalculating Thermal Diffusivity of Rock and Soil1This standard is issued under the fixed designation D4612;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method involves calculation of the thermaldiffusivity from measured values of the mass density,thermalconductivity,and specific heat at constant pressure.It isapplicable for any materials where these data can be deter-mined.The temperature range covered by this test method is293 to 573 K.This test method is closely linked to the overalltest procedure used in obtaining the primary data on density,specific heat,and thermal conductivity.It cannot be used as a“stand alone”test method because the thermal diffusivityvalues calculated by this test method are dependent on thenature of the primary data base.The test method furnishesgeneral guidelines to calculate the thermal diffusivity butcannot be considered to be all-inclusive to capture issuesrelated to the density,specific heat,and thermal conductivityNOTE1The diffusivity,as determined by this test method,is intendedto be a volume average value,with the averaging volume being 2 105m3(20 cm3).This requirement necessitates the use of specimens withvolumes greater than the minimum averaging volume and precludes use offlash methods of measuring thermal diffusivity,such as the laser pulsetechnique.1.2 The values stated in SI units are to be regarded as thestandard.No other units of measurements are included in thisstandard.1.3 This test method is intended to apply to isotropicsamples;that is,samples in which the thermal transportproperties do not depend on the direction of heat flow.If thethermal conductivity depends on the direction of heat flow,then the diffusivity derived by this test method must beassociated with the same direction as that utilized in theconductivity measurement.1.4 The thermal conductivity,specific heat,and mass den-sity measurements must be made with specimens that are asnear identical in composition and water content as possible.1.5 The generally inhomogeneous nature of geologic forma-tions precludes the unique specification of a thermal diffusivitycharacterizing an entire rock formation or soil layer.Geologicmedia are highly variable in character,and it is impossible tospecify a test method for diffusivity determination that will besuitable for all possible cases.Some of the most importantlimitations arise from the following factors:1.5.1 Variable MineralogyIf the mineralogy of the forma-tion under study is highly variable over distances on the sameorder as the size of the sample from which the conductivity,specific heat,and density specimens are cut,then the calculateddiffusivity for a given set of specimens will be dependent onthe precise locations from which these specimens were ob-tained.1.5.2 Variable PorosityThe thermal properties of porousrock or soil are highly dependent on the amount and nature ofthe porosity.A spatially varying porosity introduces problemsof a nature similar to those encountered with a spatially varyingcomposition.In addition,the character of the porosity maypreclude complete dehydration by oven drying.1.6 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.6.1 The procedure used to specify how data are collected/recorded or calculated in this standard are regarded as theindustry standard.In addition,they are representative of thesignificant digits that generally should be retained.The proce-dures used do not consider material variation,purpose forobtaining the data,special purpose studies,or any consider-ations for the users objectives;and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations.It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.1.7 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 test metis under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved May 1,2016.Published May 2016.Originallyapproved in 1986.Last previous edition approved in 2008 as D4612 08.DOI:10.1520/D4612-16.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 2.Referenced Documents2.1 ASTM Standards:2C177 Test Me