ASTM D4535-21

5.1?Information concerning the thermal expansion characteristics of rocks is important in the design of any underground excavation where the surrounding rock may be heated. Thermal strain causes thermal stresses which ultimately affect excavation stability. Examples of applications where rock thermal strain is important include: nuclear waste repositories, underground power stations, compressed air energy storage facilities, and geothermal energy facilities.

5.2?The coefficient of thermal expansion, ?, of rock is known to vary as the temperature changes. These methods provide continuous thermal strain values as a function of temperature, and therefore provide information on how the coefficient of thermal expansion changes with temperature.

5.3?Rocks are also often anisotropic, thus displaying different thermal strains depending on the orientation of strain measurement. These methods allow for measuring strain in one direction only. If anisotropy is expected, specimens with different orientations shall be prepared and tested.

1.1?These test methods cover the laboratory measurement of the one-dimensional linear thermal expansion of rocks using a dilatometer.

1.2?The methods are applicable between temperatures of 25?C to 300?C. Both bench top and confined measurement techniques are presented. Method A is used for unconfined or bench top measurements and Method B is used for confined conditions. 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 test methods shall be followed. If the results are to be reported as having been obtained by either test method, then the pertinent requirements prescribed by that test method shall be met.

1.4?These test methods do not establish details of construction and procedures 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.

1.5?UnitsThe values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8?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.