ASTM D4612-16
(Test Method)Standard Test Method for Calculating Thermal Diffusivity of Rock and Soil
Standard Test Method for Calculating Thermal Diffusivity of Rock and Soil
SIGNIFICANCE AND USE
5.1 The thermal diffusivity is a parameter that arises in the solution of transient heat conduction problems. It generally characterizes the rate at which a heat pulse will diffuse through a solid material.
5.2 The number of parameters required for solution of a transient heat conduction problem depends on both the geometry and imposed boundary conditions. In a few special cases, only the thermal diffusivity of the material is required. In most cases, separate values of k, ρ, and cp are required in addition to α. This test method provides a consistent set of parameters for numerical or analytical heat conduction calculations related to heat transport through rocks.
5.3 In order to use this test method for determination of the thermal diffusivity, the parameters (k, ρ, cp) must be determined under as near identical specimen conditions as possible.
5.4 The diffusivity determined by this test method can only be used to analyze heat transport in rock under thermal conditions identical to those existing for the k, ρ, and cp measurements.
Note 2: The quality of the result produced by this standard is dependent on 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/sampling/inspection/etc. Users of this standard 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 involves calculation of the thermal diffusivity from measured values of the mass density, thermal conductivity, and specific heat at constant pressure. It is applicable for any materials where these data can be determined. The temperature range covered by this test method is 293 to 573 K. This test method is closely linked to the overall test 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 diffusivity values calculated by this test method are dependent on the nature of the primary data base. The test method furnishes general guidelines to calculate the thermal diffusivity but cannot be considered to be all-inclusive to capture issues related to the density, specific heat, and thermal conductivity
Note 1: The diffusivity, as determined by this test method, is intended to be a volume average value, with the averaging volume being ≥ 2 × 10−5 m3 (20 cm3). This requirement necessitates the use of specimens with volumes greater than the minimum averaging volume and precludes use of flash methods of measuring thermal diffusivity, such as the laser pulse technique.
1.2 The values stated in SI units are to be regarded as the standard. No other units of measurements are included in this standard.
1.3 This test method is intended to apply to isotropic samples; that is, samples in which the thermal transport properties do not depend on the direction of heat flow. If the thermal conductivity depends on the direction of heat flow, then the diffusivity derived by this test method must be associated with the same direction as that utilized in the conductivity measurement.
1.4 The thermal conductivity, specific heat, and mass density measurements must be made with specimens that are as near identical in composition and water content as possible.
1.5 The generally inhomogeneous nature of geologic formations precludes the unique specification of a thermal diffusivity characterizing an entire rock formation or soil layer. Geologic media are highly variable in character, and it is impossible to specify a test method for diffusivity determination that will be suitable for all possible cases. Some of the most important limitations arise from the following factors:
1.5.1 Vari...
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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: D4612 − 16
Standard Test Method for
1
Calculating Thermal Diffusivity of Rock and Soil
This standard is issued under the fixed designation D4612; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.5 Thegenerallyinhomogeneousnatureofgeologicforma-
tionsprecludestheuniquespecificationofathermaldiffusivity
1.1 This test method involves calculation of the thermal
characterizing an entire rock formation or soil layer. Geologic
diffusivity from measured values of the mass density, thermal
media are highly variable in character, and it is impossible to
conductivity, and specific heat at constant pressure. It is
specify a test method for diffusivity determination that will be
applicable for any materials where these data can be deter-
suitable for all possible cases. Some of the most important
mined. The temperature range covered by this test method is
limitations arise from the following factors:
293 to 573 K. This test method is closely linked to the overall
1.5.1 Variable Mineralogy—If the mineralogy of the forma-
test procedure used in obtaining the primary data on density,
tion under study is highly variable over distances on the same
specific heat, and thermal conductivity. It cannot be used as a
order as the size of the sample from which the conductivity,
“stand alone” test method because the thermal diffusivity
specificheat,anddensityspecimensarecut,thenthecalculated
values calculated by this test method are dependent on the
diffusivity for a given set of specimens will be dependent on
nature of the primary data base. The test method furnishes
the precise locations from which these specimens were ob-
general guidelines to calculate the thermal diffusivity but
tained.
cannot be considered to be all-inclusive to capture issues
1.5.2 Variable Porosity—The thermal properties of porous
related to the density, specific heat, and thermal conductivity
rock or soil are highly dependent on the amount and nature of
NOTE1—Thediffusivity,asdeterminedbythistestmethod,isintended
the porosity. A spatially varying porosity introduces problems
−5
tobeavolumeaveragevalue,withtheaveragingvolumebeing≥2×10
3 3 ofanaturesimilartothoseencounteredwithaspatiallyvarying
m (20 cm ). This requirement necessitates the use of specimens with
composition. In addition, the character of the porosity may
volumesgreaterthantheminimumaveragingvolumeandprecludesuseof
flash methods of measuring thermal diffusivity, such as the laser pulse
preclude complete dehydration by oven drying.
technique.
1.6 All observed and calculated values shall conform to the
1.2 The values stated in SI units are to be regarded as the
guidelines for significant digits and rounding established in
standard. No other units of measurements are included in this
Practice D6026.
standard.
1.6.1 The procedure used to specify how data are collected/
1.3 This test method is intended to apply to isotropic
recorded or calculated in this standard are regarded as the
samples; that is, samples in which the thermal transport
industry standard. In addition, they are representative of the
properties do not depend on the direction of heat flow. If the
significant digits that generally should be retained. The proce-
thermal conductivity depends on the direction of heat flow,
dures used do not consider material variation, purpose for
then the diffusivity derived by this test method must be
obtaining the data, special purpose studies, or any consider-
associated with the same direction as that utilized in the
ations for the user’s objectives; and it is common practice to
conductivity measurement.
increase or reduce significant digits of reported data to be
commensuratewiththeseconsiderations.Itisbeyondthescope
1.4 The thermal conductivity, specific heat, and mass den-
of this standard to consider significant digits used in analytical
sity measurements must be made with specimens that are as
methods for engineering design.
near identical in composition and water content as possible.
1.7 This standard does not purport to address all of the
1
This test metis under the jurisdiction of ASTM Committee D18 on Soil and
safety concerns, if any, associated with its use. It is the
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
responsibility of the user of this standard to establish appro-
Current edition approved May 1, 2016. Published May 2016. Originally
priate safety and health practices and dete
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4612 − 08 D4612 − 16
Standard Practice for Test Method for
1
Calculating Thermal Diffusivity of RocksRock and Soil
This standard is issued under the fixed designation D4612; 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*
1.1 This practice involves calculation of the thermal diffusivity from measured values of the mass density, thermal conductivity,
and specific heat at constant pressure. It is applicable for any materials where these data can be determined. The temperature range
covered by this practice is 20 to 300°C.
−5 3
NOTE 1—The diffusivity, as determined by this practice, is intended to be a volume average value, with the averaging volume being ≥ 2 × 10 m
3
(20 cm ). This requirement necessitates the use of specimens with volumes greater than the minimum averaging volume and precludes use of flash
methods of measuring thermal diffusivity, such as the laser pulse technique.
NOTE 2—This practice is closely linked to the overall test procedure used in obtaining the primary data on density, specific heat, and conductivity. It
cannot be used as a “stand alone” practice because the thermal diffusivity values calculated by this practice are dependent on the nature of the primary
data base. The practice furnishes general guidelines but cannot be considered to be all-inclusive.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical
conversions to inch-pound units that are provided for information only and are not considered standard.
1.3 The practice is intended to apply to isotropic samples; that is, samples in which the thermal transport properties do not
depend on the direction of heat flow. If the thermal conductivity depends on the direction of heat flow, then the diffusivity derived
by this practice must be associated with the same direction as that utilized in the conductivity measurement.
1.4 The thermal conductivity, specific heat, and mass density measurements must be made with specimens that are as near
identical in composition and water content as possible.
1.5 The generally inhomogeneous nature of geologic formations precludes the unique specification of a thermal diffusivity
characterizing an entire rock formation. Geologic media are highly variable in character, and it is impossible to specify a practice
for diffusivity determination that will be suitable for all possible cases. Some of the most important limitations arise from the
following factors:
1.5.1 Variable Mineralogy—If the mineralogy of the formation under study is highly variable over distances on the same order
as the size of the sample from which the conductivity, specific heat, and density specimens are cut, then the calculated diffusivity
for a given set of specimens will be dependent on the precise locations from which these specimens were obtained.
1.5.2 Variable Porosity—The thermal properties of porous rock are highly dependent on the amount and nature of the porosity.
A spatially varying porosity introduces problems of a nature similar to those encountered with a spatially varying composition. In
addition, the character of the porosity may preclude complete dehydration by oven drying.
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.7 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
C177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded-Hot-Plate Apparatus
C518 Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
1
This practice istest metis under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved July 1, 2008May 1, 2016. Published July 2008May 2016. Originally approved in 1986. Last previous edition approved in 20032008 as
D4612 – 03.D4612 – 08. DOI: 10.1520/D4612-08.10.1520/D4612-16.
2
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