MESO-FAILURE MECHANISM OF ROCK UNDER THERMAL-MECHANICAL COUPLING EFFECTS

摘要

The meso-failure mechanism of rock under thermal-mechanical coupling effects has been investigated in-situ through Scanning Electron Microscopy (SEM). Some failure phenomena, such as brittle fracture of sandstone could occur in two places, different minerals bear independently, brittle cracks of sandstone under thermal-mechanical coupling effects can also bifurcate, had clearly been reported. A lot of micro-cracks or branch cracks near the main crack had been observed when the test temperature was below 100°C. However, when the temperature was over 125!, thermal activation of sandstone internal local zone would increase, and the ability to resist deformation and coordination has been strengthened. In addition, there were few cracks or secondary cracks near the main crack. From 25°C to 300°C, fracture toughness of sandstone will increase firstly and then decrease, and 150! is the threshold temperature of fracture toughness of sandstone at meso-scale. With the increasing of temperature, sandstone failure mechanism will transfer from brittle to ductility mechanism. Sandstone failure was affected by many fracture mechanism, such as transgranular fracture, intracrystalline fracture and mixed mode fracture. The deformation field of sandstone, which was obtained through SEM micro-measurement, was measured using Digital Speckle Correlation Method (DSCM).