Effect of thermal damage on tensile strength and microstructure of granite: a case study of Beishan, China

The physical and mechanical properties of surrounding rock of high level radioactive waste repository are affected by the heat released by nuclide decay. In this paper, the effects of temperature on P-wave velocity, porosity and tensile strength are investigated, the microstructure of the specimens with different temperature is observed utilizing a polarizing microscope. Brazilian splitting tests on the heated specimens combined with the acoustic emission technology to monitor the rock deformation and failure. It is observed that the P-wave velocity of granite decreases with the increase of temperature. The porosity of granite changes with temperature and has obvious threshold that is the porosity of granite will increase rapidly when the temperature exceeds 500 °C. Besides, the tensile strength of granite shows a linear decrease with the increasing temperature. The results of acoustic emission tests and thin section observations indicate that temperature leads to an increase in the closure and unstable extension of cracks. The findings of the present research can provide reference for construction safety of the rock mass subjected to high temperature.