Experimental characterisation of thermo-mechanical coupling properties of Beishan granite

With the help of MTS815 rock mechanics test system and 3D acoustic emission monitoring system, a series of thermo-mechanical coupling tests at temperatures in the range of 23-90 degrees C and confining pressures from 5 to 30 MPa are carried out, to investigate the thermo-mechanical properties of Beishan granite. The granite is taken from Beishan site, the most potential area for the China's high-level radioactive waste repository. The experimental results indicate that the mechanical behaviour and crack characteristics are essential related to the coupling effect of temperature and confining pressure. The mechanical characteristics such as elastic modulus, crack damage stress and rock failure strength are degraded slightly with the increase of temperature. In accordance with the degradation of mechanical properties, high temperature leads to the development of new microcracks or propagation of pre-existing microcracks within the rocks, which can be revealed by the increase of the AE activities. Rock specimen tends to become more stable under high confining pressure. A brittle-ductile mechanical behaviour transition of Beishan granite can be observed, especially under a high confining pressure.