ASTM D5335-14 PDF Download

The ASTM D5335-14 standard provides a procedure for measuring the thermal expansion characteristics of rocks. The information obtained from this test is important for the design of underground excavations where the temperature of the surrounding rock may change and cause thermal strain and stress that can affect the stability of the excavations. Some specific applications where knowledge of rock thermal strain is important include nuclear waste repositories, underground power stations, compressed air energy storage facilities, energy foundations, and geothermal energy facilities.

The test method described in this standard allows for the continuous monitoring of thermal strain as a function of temperature. It is important to note that the coefficient of linear thermal expansion, a, of rock is known to vary as the temperature changes, and the thermal strain is not always a linear function of temperature. The standard identifies that other methods of measuring the coefficient of linear thermal expansion of rock by averaging the thermal strain over a temperature range may result in failure to determine the variation in a due to reasons such as non-linearity of a with temperature, anisotropy of rocks, and the possibility of negative and positive values of a in different directions.

This standard mentions that both wire and foil type strain gauges have been successfully used to measure the thermal expansion coefficients of rock. These coefficients are usually very small, on the order of millionths of a millimeter per millimeter per degree Celsius. Therefore, measurement methods for rocks require greater precision than those used for plastics and metals. The standard also emphasizes that the quality of the results obtained using this method depends on the competence of the personnel performing the test and the suitability of the equipment and facilities used.