ASTM D4535-85(2004)
(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 2004)
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 E228 Test Method for Linear Thermal Expansion of Solid
Materials with Vitreous a Silica Dilatometer
1.1 Thesetestmethodscoverthelaboratorymeasurementof
the linear (one-dimensional) thermal expansion of rocks using
3. Terminology
a dilatometer.
3.1 Definitions of Terms Specific to This Standard:
1.2 Thesetestmethodsareapplicablebetweentemperatures
3.1.1 sample thermal strain, e— change in length of a unit
t
of 25°C to 300°C. Both bench top and confined measurement
length of sample when the sample is subjected to heat. The
techniques are presented. Rocks of varying moisture content
mathematical expression is:
can be tested.
1.3 For satisfactory results in conformance with these test e 5 ~L 2 L !/L (1)
t 2 1 0
methods, the principles governing the size, construction, and
where:
use of the apparatus described in these methods should be
L and L = specimen lengths corresponding to tempera-
1 2
followed. If the results are to be reported as having been
tures T and T , and
1 2
obtained by this method, then all pertinent requirements
L = the original specimen length at some refer-
prescribed in this method shall be met.
ence temperature T .
1.4 These test methods do not establish details of construc-
Thermal strain is also equal to the specimen thermal dis-
tion and procedure to cover all test situations that might offer
placement, d, divided by the original sample length:
t
difficultiestoapersonwithouttechnicalknowledgeconcerning
e 5d/L (2)
the theory of heat flow, temperature measurement, and general t t 0
testing practices. Standardization of these test methods does
3.1.2 mean coeffıcient of linear expression, a —between
m
not reduce the need for such technical knowledge. It is
two temperatures, T and T , is defined as follows:
1 2
recognized also that it would be unwise, because of the
a 5 ~L 2 L !/[L ~T 2 T !# (3)
m 2 1 0 2 1
standardization of this method, to resist in any way the further
development of improved or new methods or procedures by
where:
research workers. L and L = specimen lengths at temperatures T and T ,
1 2 1 2
1.5 This standard does not purport to address all of the respectively. Therefore, a is obtained by
m
safety concerns, if any, associated with its use. It is the dividing the linear thermal strain, (L − L )/
1 2
responsibility of the user of this standard to establish appro- L , by the change in temperature units are
inch/inch or centimetre/centimetre per tem-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. perature change in °F or °C, respectively. a
m
is often expressed in parts per million per
2. Referenced Documents
degree.
2.1 ASTM Standards:
3.1.3 Uponheating( T > T ),anincreaseinthelengthofthe
2 1
E83 Practice for Verification and Classification of Exten- rock sample will give a positive value of a . If a decrease in
m
someters
length (contraction) is observed, a will become negative.
m
4. Summary of Test Methods
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD18onSoil
4.1 The application of heat to a rock causes it to expand.
and Rock and are the direct responsibility of Subcommittee D18.12 on Rock
This expansion divided by the original length of the rock
Mechanics.
Current edition approved Nov. 1, 2004. Published December 2004. Originally
specimens is the thermal strain from which coefficients of
approved in 1985. Last previous edition approved in 2000 as D4535–85(2000)
expansioncanbecalculated.Thisstandardcoverstwomethods
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standardsvolume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4535 – 85 (2004)
formeasuringrockexpansion.Theprimarydifferencebetween 5.3 Rocks are also often anisotropic, thus displaying differ-
the two methods is in the type of dilatometer used. ent thermal strains depending on the orientation of strain
4.1.1 Test Method I—Test Method I is the procedure used measurement.Thesemethodsallowformeasuringstraininone
when making unconfined or bench top measurements. The directiononly.Ifanisotropyisexpected,sampleswithdifferent
method and apparatus are similar to that described in Test orientations should be prepared and tested.
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.
6. Apparatus
6.1 Dilatometer:
6.1.1 Method I—The dilatometer used for bench measure-
mentsmaybeofthetubeorrodtype,asshowninFig.1.Those
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 PracticeE83).
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
FIG. 1 Apparatus Commonly Used to Perform Bench Top (Method
I) Thermal Expansion Measurements averaged.
D 4535 – 85 (2004)
FIG. 2 Apparatus Commonly Used to Perform Confined (Method II) Thermal Expansion Measurements
6.3 Furnace—The furnace shall be large enough to contain 7. Sampling
the specimen and apparatus and maintain uniform temperature
7.1 Thenumberandtypesofrockcorestesteddependpartly
along the axis of the specimen with variations no greater than
on the intended application of the test results. For example, an
61°C.Themeansampletemperatureshallbecontrolledwithin
initial mechanical characterization of a site might require
61°C. The use of a programmable temperature controller that
several samples from a variety of formations, while a detailed
canslowlyincreaseordecreasesampletemperaturesatratesat
thermo-mechanical investigation of a particular location may
least as low as 0.1°C/min is recommended.
require many rock tests from a single formation. The final
6.4 Temperature Measuring Instruments— Thermocouples
testing program will depend on the technical judgment and the
or platinum resistant thermometers are recommended. The
experience of project personnel.
exact type will depend on the temperature range of interest. In
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
in machine shop practice is satisfactory.
D 4535 – 85 (2004)
7.3 Moisture Condition of Samples— The moisture condi- 10.3 Repeat the standardization test procedure three times,
tion of the rock can influence the measured thermal expansion. starting from the same initial condition, to verify the repeat-
Test the specimens in a manner that best simulates the in situ ability of the dilatometer. Variation from run to run should be
conditions of interest. For natural conditions, the moisture no greater than 5 %.
content of the rock core and the chemical characteristics of the 10.4 Thecalculatedexpansionofthecalibrationspecimenis
pore fluid shall be preserved between the time of recovery and subtracted from the calibration expansion results as follows:
testing; then determine the moisture content of core material
d 5d 2d ; (4)
2 1 s
contiguous to the test specimen.
where:
7.4 Anisotropy—The thermal expansion coefficient of many
d 5a·l·DT (5)
rocks is different along various axes of the rock. Measure the s
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
each sample is recorded. Note the orientation of each sample
d = thermal expansion of the calibration specimen, cm
s
onthesampleandcarrysuitablemarkingsthrougheachcutting
a = coefficient of linear expansion for the calibration
until the final specimen is ready for testing. These markings
specimen,
shouldindicatecompassdirectionandup/downdirections,and
l = gage length of the calibration specimen, cm, and
other orientation with respect to geologic structures.
DT = temperaturedifferencebetweenareferencetempera-
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-
ometry is a right circular cylinder. The specific recommended
10.5 The thermal expansion of the apparatus should be less
dimensions for Method I are given in Test Method E228. For
than 20 % of the measured thermal expansion of the rock. The
Method II, the sample should be a right circular cylinder with
measured thermal expansion of the apparatus shall be reported
a length to diameter ratio of 2 to 1. For both methods the
as specified in Section 14.
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
9.1 Do not degrade the rock during machining. Prevent
actual testing unless drying is specified, in which case drying
mechanical and fracture damage to the rock fabric by appro-
shall be performed in accordance with 9.2.
priately slow machining processes and the use of proper
coolant. Select coolant fluids based upon chemical compatibil-
12. Procedure
ity with the rock; for example, tap water may be adequate for
12.1 Cleanthesamplewithanon-chemicalreactivesolvent,
granite, whereas a saturated brine or mineral oil may be best
such as acetone, and install the sample in the dilatometer.Take
for salt.
special care to ensure that the end surfaces of the specimen are
9.2 Drying—Ifthesampleistobetesteddry,dryat80°Cin
free from foreign particles. If confined experiments are to be
a vacuum oven for 24 h.At no time during the drying process
performed (Method II), jacket the specimen with an appropri-
shallthesamplebesubjectedtoheatingorcoolingratesgreater
ate heat resistant jacketing material to prevent confining fluid
than 1°C/min.
intrusion (Note 1). Install all temperature measuring instru-
9.2.1 An alternative drying schedu
...
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