ASTM D4612-86(1996)

Standard Practice for Calculating Thermal Diffusivity of Rocks

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.  Note 1-The diffusivity, as determined by this practice, is intended to be a volume average value, with the averaging volume being [>=] 2 X 10  m  (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 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.  
1.3 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.  
1.4 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:  
1.4.1 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.
1.4.2 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.  
1.5 This standard does not purport to address all of the safety problems asssociated 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.

General Information

• Status: Historical
• Publication Date: 09-May-1996
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.12 - Rock Mechanics

Relations

• Replaced By: ASTM D4612-03 - Standard Practice for Calculating Thermal Diffusivity of Rocks
• Effective Date: 10-Jun-2003
• Referred By: ASTM C1470-20 - Standard Guide for Testing the Thermal Properties of Advanced Ceramics
• Effective Date: 10-May-1996

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 4612 – 86 (Reapproved 1996)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Calculating Thermal Diffusivity of Rocks
This standard is issued under the fixed designation D 4612; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.4.2 Variable Porosity—The thermal properties of porous
rock are highly dependent on the amount and nature of the
1.1 This practice involves calculation of the thermal diffu-
porosity. A spatially varying porosity introduces problems of a
sivity from measured values of the mass density, thermal
nature similar to those encountered with a spatially varying
conductivity, and specific heat at constant pressure. It is
composition. In addition, the character of the porosity may
applicable for any materials where these data can be deter-
preclude complete dehydration by oven drying.
mined. The temperature range covered by this practice is 20 to
1.5 This standard does not purport to address all of the
300°C.
safety concerns, if any, associated with its use. It is the
NOTE 1—The diffusivity, as determined by this practice, is intended to
responsibility of the user of this standard to establish appro-
−5
be a volume average value, with the averaging volume being $ 2 3 10
priate safety and health practices and determine the applica-
3 3
m (20 cm ). This requirement necessitates the use of specimens with
bility of regulatory limitations prior to use.
volumes greater than the minimum averaging volume and precludes use of
flash methods of measuring thermal diffusivity, such as the laser pulse
2. Referenced Documents
technique.
NOTE 2—This practice is closely linked to the overall test procedure
2.1 ASTM Standards:
used in obtaining the primary data on density, specific heat, and conduc-
C 177 Test Method for Steady-State Thermal Transmission
tivity. It cannot be used as a “stand alone” practice because the thermal 2
Properties by Means of the Guarded Hot Plate
diffusivity values calculated by this practice are dependent on the nature
C 351 Test Method for Mean Specific Heat of Thermal
of the primary data base. The practice furnishes general guidelines but
Insulation
cannot be considered to be all-inclusive.
C 518 Test Method for Steady-State Thermal Transmission
1.2 The practice is intended to apply to isotropic samples;
Properties by Means of the Heat Flow Meter
that is, samples in which the thermal transport properties do not
C 642 Test Method for Specific Gravity, Absorption, and
depend on the direction of heat flow. If the thermal conductiv-
Voids in Hardened Concrete
ity depends on the direction of heat flow, then the diffusivity
D 2766 Test Method for Specific Heat of Liquids and
derived by this practice must be associated with the same
Solids
direction as that utilized in the conductivity measurement. 5
D 4611 Test Method for Specific Heat of Rock and Soil
1.3 The thermal conductivity, specific heat, and mass den-
sity measurements must be made with specimens that are as
3. Terminology
near identical in composition and water content as possible.
3.1 Parameter Definitions:
1.4 The generally inhomogeneous nature of geologic forma-
3.1.1 mass density—the mass of the sample per unit volume
tions precludes the unique specification of a thermal diffusivity 3
of sample, r(kg/m ).
characterizing an entire rock formation. Geologic media are
3.1.2 instantaneous specific heat—the rate of change of
highly variable in character, and it is impossible to specify a
specimen enthalpy per unit mass, h, with respect to tempera-
practice for diffusivity determination that will be suitable for
ture, T, at constant pressure,
all possible cases. Some of the most important limitations arise
p, c 5 ~dh/dT!
p p
from the following factors:
1.4.1 Variable Mineralogy—If the mineralogy of the forma-
3.1.3 thermal conductivity—the constant of proportionality,
tion under study is highly variable over distances on the same
k, relating the vector heat flux, → F expressed in watts per
order as the size of the sample from which the conductivity,
square metre, to the temperature gradient, „T, → F5 −k„T.
specific heat, and density specimens are cut, then the calculated
The thermal conductivity may be a function of the direction of
diffusivity for a given set of specimens will be dependent on
→ F and the temperature, T. The units of k are W/m−K.
the precise locations from which these specimens were ob-
tained.
Annual Book of ASTM Standards, Vol 04.06.
1 3
This practice is under the jurisdiction of ASTM Committee D-18 on Soil and Annual Book of ASTM Standards, Vol 04.02.
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics. Annual Book of ASTM Standards, Vol 05.02.
Current edition approved Sept. 26, 1986. Published November 1986. Annual Book of ASTM Standards, Vol 04.08.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4612
3.1.4 thermal diffusivity—the thermal diffusivity, a,isa 6.2.1.1 Determine the mass of the specimen, m,onan
s
derived parameter. It is related to r, c , and k by the relation, analytical balance and the volume, V , by measurement of
p s
sample dimensions or by water displacement (immersion). If
a5 k/rc
p
the volume is measured by immersion, the specimen must be
The units of a are m /s.
encapsulated in a waterproof flexible container of negligible
3.2 Definitions of Terms Specific to This Standard:
volume compared to the specimen volume. Record the density,
3.2.1 sample—a sample is a large piece of rock from which
as follows,
the specimens used in the k, r, and c measurements are
p
r5 m /V (1)
s s
obtained. Usually the samples are obtained in the form of cores
from a drilling operation.
where:
3.2.2 specimens—the specimens are pieces cut from the
m 5 specimen mass, and
s
sample for the k, r, and c measurements. Their sizes and
p V 5 specimen volume.
s
shapes are governed by the applicable ASTM standards listed
Also estimate the accuracy of the r determination from the
in 2.1.
uncertainties associated with the m and V measurements.
s s
6.2.1.2 Measure the specimen specific gravity using Test
4. Summary of Practice
Method C 642. In situations where the measurement is to be
4.1 The thermal diffusivity is determined from the equation
made at temperatures near or above the boiling point of water,
in 3.1.4. The data for k and c must be available over the
p
a suitable oil working fluid may be substituted for water in this
temperature range of interest. For density, r, a single measure-
procedure. Determine the density, r, by multiplying the spe-
ment at room temperature may be used because the density is
cific gravity by the density of the working fluid at the
approximately constant over the 20 to 300°C temperature
immersion temperature.
range covered by this practice.
6.2.2 Measure the specimen specific heat using Test Method
4.2 The measurements of k, r, and c are to be performed
p
D 4611.
using the test methods in Section 6.
6.2.3 Measure the specimen conductivity using Test Method
5. Significance and Use C 518 or Test Method C 177.
5.1 Th
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