Mechanical and electrical responses of natural-cooled high-temperature granite of different grain sizes

Abstract

In order to understand the effect of grain size on the mechanical and electrical responses of natural-cooled high-temperature granite, uniaxial compression tests were carried out on natural cooled coarse- and fine-grained granite samples subjected to thermal treatment at room temperature, 200 °C, 400 °C, and 600 °C respectively. The resistivity and acoustic emission (AE) during the compression were monitored and changes in physical and mechanical properties, the AE and resistivity characteristics in the loading process were analyzed. Results show that high temperature exerts a more significant effect on deteriorating the coarse-grained granite. Changes in resistivity can reflect the development of rock damage. Corresponding to the compaction stage, crack initiation and stable propagation stage, and crack rapid propagation stage of rock under compressive load, changes in resistivity can be divided into three stages accordingly, including the initial rapid descent stage, the gentle descent stage, and the secondary rapid descent stage for the thermal-treated rock at 25–400 °C. The secondary rapid descent stage of resistivity can be used as a precursor for rock entering into the failure stage. The resistivity change is more sensitive to the damage development in coarse-grained granite.