ASTM D4535-85(2000)
(Test Method)Standard Test Methods for Measurement of Thermal Expansion of Rock Using a Dilatometer
Standard Test Methods for Measurement of Thermal Expansion of Rock Using a Dilatometer
SCOPE
1.1 These test methods cover the laboratory measurement of the linear (one-dimensional) thermal expansion of rocks using a dilatometer.
1.2 These test methods are applicable between temperatures of 25oC to 300oC. Both bench top and confined measurement techniques are presented. Rocks of varying moisture content can be tested.
1.3 For satisfactory results in conformance with these test methods, the principles governing the size, construction, and use of the apparatus described in these methods should be followed. If the results are to be reported as having been obtained by this method, then all pertinent requirements prescribed in this method shall be met.
1.4 These test methods do not establish details of construction and procedure to cover all test situations that might offer difficulties to a person without technical knowledge concerning the theory of heat flow, temperature measurement, and general testing practices. Standardization of these test methods does not reduce the need for such technical knowledge. It is recognized also that it would be unwise, because of the standardization of this method, to resist in any way the further development of improved or new methods or procedures by research workers.
1.5 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.
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Designation: D 4535 – 85 (Reapproved 2000)
Standard Test Methods for
Measurement of Thermal Expansion of Rock Using a
Dilatometer
This standard is issued under the fixed designation D4535; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 Thesetestmethodscoverthelaboratorymeasurementof 3.1 Definitions of Terms Specific to This Standard:
the linear (one-dimensional) thermal expansion of rocks using 3.1.1 sample thermal strain, e— change in length of a unit
t
a dilatometer. length of sample when the sample is subjected to heat. The
1.2 Thesetestmethodsareapplicablebetweentemperatures mathematical expression is:
of 25°C to 300°C. Both bench top and confined measurement
e 5 ~L 2 L !/L (1)
t 2 1 0
techniques are presented. Rocks of varying moisture content
can be tested. where:
L and L = specimen lengths corresponding to tempera-
1.3 For satisfactory results in conformance with these test
1 2
tures T and T , and
methods, the principles governing the size, construction, and
1 2
L = the original specimen length at some refer-
use of the apparatus described in these methods should be 0
ence temperature T .
followed. If the results are to be reported as having been 0
Thermal strain is also equal to the specimen thermal dis-
obtained by this method, then all pertinent requirements
placement, d, divided by the original sample length:
prescribed in this method shall be met. t
1.4 These test methods do not establish details of construc-
e 5d/L (2)
t t 0
tion and procedure to cover all test situations that might offer
3.1.2 mean coeffıcient of linear expression, a —between
m
difficultiestoapersonwithouttechnicalknowledgeconcerning
two temperatures, T and T , is defined as follows:
1 2
the theory of heat flow, temperature measurement, and general
a 5 ~L 2 L !/@L ~T 2 T !# (3)
m 2 1 0 2 1
testing practices. Standardization of these test methods does
not reduce the need for such technical knowledge. It is
where:
recognized also that it would be unwise, because of the
L and L = specimen lengths at temperatures T and T ,
1 2 1 2
standardization of this method, to resist in any way the further
respectively. Therefore, a is obtained by
m
development of improved or new methods or procedures by
dividing the linear thermal strain, (L − L )/
1 2
research workers.
L , by the change in temperature units are
1.5 This standard does not purport to address all of the
inch/inch or centimetre/centimetre per tem-
safety concerns, if any, associated with its use. It is the
perature change in °F or °C, respectively. a
m
responsibility of the user of this standard to establish appro-
is often expressed in parts per million per
priate safety and health practices and determine the applica-
degree.
bility of regulatory limitations prior to use.
3.1.3 Uponheating( T > T ),anincreaseinthelengthofthe
2 1
rock sample will give a positive value of a . If a decrease in
m
2. Referenced Documents
length (contraction) is observed, a will become negative.
m
2.1 ASTM Standards:
E83 Practice for Verification and Classification of Exten- 4. Summary of Test Methods
someters
4.1 The application of heat to a rock causes it to expand.
E228 Test Method for Linear Thermal Expansion of Solid
This expansion divided by the original length of the rock
Materials with Vitreous a Silica Dilatometer
specimens is the thermal strain from which coefficients of
expansioncanbecalculated.Thisstandardcoverstwomethods
formeasuringrockexpansion.Theprimarydifferencebetween
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD18onSoil
the two methods is in the type of dilatometer used.
and Rock and are the direct responsibility of Subcommittee D18.12 on Rock
Mechanics.
4.1.1 Test Method I—Test Method I is the procedure used
Current edition approved Oct. 25, 1985. Published December 1985.
when making unconfined or bench top measurements. The
Annual Book of ASTM Standards, Vol 03.01.
method and apparatus are similar to that described in Test
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4535
Method E228. The rock specimen thermal displacement is 5.4 Careshouldbeexercisedintheinterpretationofthermal
measured using a dilatometer as shown in Fig. 1. The sample strain data of rocks with significant moisture content. Under
displacement is measured by a transducer located outside the certain temperature and pressure conditions, steam may be
heated area of the sample; therefore, apparent strain due to producedintheporespace.Steammaycauseerrorsbecauseof
apparatus expansion and contraction is minimized. microcrack production or changes in the pore pressure. The
4.1.2 Test Method II—Test Method II employs a dilatomet- phase change from water to steam in the pore space can result
ric device which is located inside the heated zone, as shown in in several phenomena which complicate data analysis, as
Fig. 2. This test method is most suited for the measurement of follows:
rock thermal strain under confined conditions.
5.4.1 Evolved steam may change the pore pressure and thus
4.2 In both test methods, sample expansion is measured the effective stress in the rock, resulting in anomalous strain
continuously as temperature is gradually increased or allowed readings.
to stabilize at discrete temperature points. 5.4.2 Losing all the moisture may dehydrate clays in the
pore space and thus change expansion characteristics, espe-
5. Significance and Use
cially in layered rocks.
5.1 Information concerning the thermal expansion charac-
5.5 The researcher using this standard must use best judg-
teristics of rocks is important in the design of any underground
mentastohowtomakethethermalexpansionmeasurementso
excavation where the surrounding rock may be heated. Ther-
that it accurately represents the conditions in the field.
mal strain causes thermal stresses which ultimately affect
5.6 Method II is amenable to confined thermal strain deter-
excavation stability. Examples of applications where rock
minations. Confined tests may be most appropriate when:
thermal strain is important include: nuclear waste repositories,
5.6.1 Pore pressure must be imposed in the pore space to
underground power stations, compressed air energy storage
maintain the liquid phase of water through the desired tem-
facilities, and geothermal energy facilities.
perature range.
5.2 The coefficient of thermal expansion or “alpha” or rock
5.6.2 The thermal strain of the rock is sensitive to confining
is known to vary as the temperature changes. These methods
stress.
provide continuous thermal strain values as a function of
5.6.3 Thesampleisfragileorfriable,orboth,andcannotbe
temperature, and therefore provide information on how alpha
machined into the shapes required for Method I.
changes with temperature.
5.3 Rocks are also often anisotropic, thus displaying differ-
6. Apparatus
ent thermal strains depending on the orientation of strain
6.1 Dilatometer:
measurement.Thesemethodsallowformeasuringstraininone
6.1.1 Method I—The dilatometer used for bench measure-
directiononly.Ifanisotropyisexpected,sampleswithdifferent
mentsmaybeofthetubeorrodtype,asshowninFig.1.Those
orientations should be prepared and tested.
components of the dilatometer exposed to elevated tempera-
tures should be fabricated of materials with coefficients of
linear expansion that are as small as practicable.
6.1.2 Method II—In Method II the entire dilatometer is
exposed to elevated temperature. Therefore, transducers, rods,
and other components should be fabricated of materials with
low thermal expansions (for example, fused silica, super
invar). When the apparatus is tested with a quartz calibration
specimen, the apparatus strain should be less than 20 % of the
anticipated rock strain (refer to Fig. 2).
6.2 Extensometer—Extensometers measure length change.
In principle, any accurate length measuring device with good
long-termstabilitymaybeused;thisincludesdialgages,linear
variable differential transducers, or capacitive transducers.
Whicheverdeviceisselected,itmusthavesufficientresolution
to measure 0.01 % sample strain (Refer to Practice E83).
6.2.1 ThosedevicesusedinMethodIImustbefabricatedof
materials that allow direct exposure of the device to the
anticipated temperature. Also, transducer bodies should be
vented for operation in a pressure environment. At least two
transducers are used, as shown in Fig. 2, and their outputs
averaged.
6.3 Furnace—The furnace shall be large enough to contain
the specimen and apparatus and maintain uniform temperature
along the axis of the specimen with variations no greater than
61°C.Themeansampletemperatureshallbecontrolledwithin
FIG. 1 Apparatus Commonly Used to Perform Bench Top (Method
I) Thermal Expansion Measurements 61°C. The use of a programmable temperature controller that
D 4535
FIG. 2 Apparatus Commonly Used to Perform Confined (Method II) Thermal Expansion Measurements
canslowlyincreaseordecreasesampletemperaturesatratesat several samples from a variety of formations, while a detailed
least as low as 0.1°C/min is recommended.
thermo-mechanical investigation of a particular location may
6.4 Temperature Measuring Instruments— Thermocouples
require many rock tests from a single formation. The final
or platinum resistant thermometers are recommended. The
testing program will depend on the technical judgment and the
exact type will depend on the temperature range of interest. In
experience of project personnel.
general, the temperature should be measured to within 60.5°C
7.2 Statistical Requirements—It is recommended that the
with a resolution of at least6 0.2°C. Make measurements at
number of samples tested be sufficient to provide an adequate
threelocationsontheaxisofthesample,oneneareachendand
statistical basis for evaluation of the results. Rock types which
one at the sample midpoint.
are highly variable would require more tests than relatively
6.5 Micrometer—Calipers should have an index permitting
uniform rocks, in order to evaluate the results with equal
direct reading of 0.025 mm for measuring the initial length of
certainty.
thespecimen.Ahighgradescrewmicrometercustomarilyused
7.3 Moisture Condition of Samples— The moisture condi-
in machine shop practice is satisfactory.
tion of the rock can influence the measured thermal expansion.
7. Sampling
Test the specimens in a manner that best simulates the in situ
conditions of interest. For natural conditions, the moisture
7.1 Thenumberandtypesofrockcorestesteddependpartly
content of the rock core and the chemical characteristics of the
on the intended application of the test results. For example, an
initial mechanical characterization of a site might require pore fluid shall be preserved between the time of recovery and
D 4535
d 5d 2d ; (4)
testing; then determine the moisture content of core material
2 1 s
contiguous to the test specimen.
where:
7.4 Anisotropy—The thermal expansion coefficient of many
d 5a·l·DT (5)
s
rocks is different along various axes of the rock. Measure the
thermal expansion in several directions in order to assess the
where:
degree of anisotropy. d = thermal expansion of the test apparatus, cm,
7.5 Documentation—Since the thermal expansion of most d = apparent thermal expansion measured by the appa-
rock is anisotropic, it is important that the field orientation of ratus, cm
d = thermal expansion of the calibration specimen, cm
each sample is recorded. Note the orientation of each sample
s
a = coefficient of linear expansion for the calibration
onthesampleandcarrysuitablemarkingsthrougheachcutting
specimen,
until the final specimen is ready for testing. These markings
l = gage length of the calibration specimen, cm, and
should indicate compass direction and up/down directions, and
DT = temperaturedifferencebetweenareferencetempera-
other orientation with respect to geologic structures.
ture (room temperature or slightly elevated above
8. Test Specimens
room temperature) and an elevated temperature, °C.
8.1 Dimension and Geometry—In general, the proper ge-
10.5 The thermal expansion of the apparatus should be less
ometry is a right circular cylinder. The specific recommended
than 20 % of the measured thermal expansion of the rock. The
dimensions for Method I are given in Test Method E228. For
measured thermal expansion of the apparatus shall be reported
Method II, the sample should be a right circular cylinder with
as specified in Section 14.
a length to diameter ratio of 2 to 1. For both methods the
minimum dimension should be 10 times the largest grain size.
11. Preconditioning
9. Preparation
11.1 Rock samples shall not be thermally cycled before the
actual testing unless drying is specified, in which case drying
9.1 Do not degrade the rock during machining. Prevent
shall be performed in accordance with 9.2.
mechanical and fracture damage to the rock fabric by appro-
priately slow machining processes and the use of proper
12. Procedure
coolant. Select coolant fluids based upon chemical compatibil-
12.1 Cleanthesamplewithanon-chemicalreactivesolvent,
ity with the rock; for example, tap water may be adequate for
such as acetone, and install the sample in the dilatometer.Take
granite, whereas a saturated brine or mineral oil may be best
special care to ensure that the end surfaces of the specimen are
for salt.
free from foreign particles. If confined experiments are to be
9.2 Drying—If the sample is to be tested dry, dry at 80°C in
performed (Method II), jacket the specimen with an appropri-
a vacuum oven for 24 h.At no time during the drying process
ate heat resistant jacketing material to prevent confining fluid
shallthesamplebesubjectedtoheatingorcoolingratesgreater
intrusion (Note 1). Install all temperature measuring instru-
than 1°C/min.
mentation and insert the specimen into the furnace. Heat the
9.2.1 An alternative drying schedule may be used in those
specimen in accordance with one of the following thermal
instances where a vacuum oven is not available and it is not of
schedules, A or B (Note 2):
interest to know the test specimen response to the first
application of heat. In such a case, heat the specimen to 105 6
NOTE 1—Silicone elastomers are often used for jacketing material.
2°C at a rate not greater than 1°C/min. Maintain this tempera-
NOTE 2—In general, Schedule A results in greater accuracy. It is more
ture for at least 24 h. Cool
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