Three-dimensional numerical study on failure mechanism of granite after thermal treatment based on moment tensor inversion

Abstract

In this study, a three-dimensional model was established to study the failure mechanism of granite after thermal treatment. Firstly, the evolution of micro-cracks and thermal stress in the sample was quantitatively analyzed, and the evolution of acoustic emission events under different stress levels was discussed. Then, combined with moment tensor inversion, the influence of temperature on the failure type of acoustic emission source was determined. The results show that: (1) High temperature increases the anisotropy of rock, and the thermal stress leads to the development of micro-cracks; (2) At 25 °C∼450 °C, the magnitude of acoustic emission events is concentrated in −5.83∼4.23, and it in this temperature range is characterized of high damage intensity and high release energy. Above 450 °C, the magnitude is concentrated in −5.33∼6.23, b value changes in 2.1∼4.11, the development of micro-cracks becomes disordered. There is a negative exponential relationship between acoustic emission events and the number of micro-cracks; (3) The distribution of acoustic emission source types obtained from 2D and 3D models is consistent, the b value obtained by the 2D model is larger than that of the 3D model, which overestimates the temperature damage to the sample’s mechanical properties.