Study on thermal damage mechanism and energy evolution characteristics of granite after high temperature based on discrete element method

Abstract

In order to explore the thermal cracking behavior and energy conversion mechanism of granite at different temperatures from a mesoscopic perspective. Based on the laboratory experimental, PFC2D was used to construct different particle cluster model for research. The mechanical properties of granite under uniaxial compression under laboratory experimental and numerical simulation were compared and analyzed. The evolution laws of microcracks and particle displacement during high temperature treatment were explored. The relationship between energy conversion mechanism and crack evolution of granite after exposure to different temperatures was emphatically analyzed. The results show that: the stress-strain curve of laboratory experimental and the stress-strain curve under numerical simulation have similar evolution laws, the relative error between the numerical simulation results of peak strength and laboratory experimental is less than 5%, and the relative error of elastic modulus is less than 10%. The higher the temperature, the more thermal induced cracks are produced and the larger the particle displacement is. The cracks and particle displacement during heating are larger than those during cooling. Thermal induced cracks are mainly intra-granular tension, and when T ≥ 600 ℃, the shear cracks appear. The storage of elastic energy and the slow dissipation of energy are the main factors before the granite peak, and the dissipation energy increases abruptly after the peak, and the elastic strain energy is released rapidly. The higher the temperature, the more the number of microcracks before the peak of granite, and the greater the damage degree before the peak. Therefore, the weaker the energy storage property, the stronger the energy release property, and the easier the energy driven destruction.