Dynamic mechanical characteristics of post-peak sandstone under three-dimensional cyclic impact
Authors: ZHANG Jun-wen, ZHANG Yang, LI Shi-fang, SONG Zhi-xiang, DONG Xu-kai, WU Shao-kang, FAN Wen-bing, ZHOU Yan, SANG Pei-miao, LI Ning
At present, the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress, and secondary rock burst disaster is prone to occur under complex stress disturbance. According to incomplete statistics, as of 2023, 80% of coal mine rock bursts accidents in China occur in mining roadway. In view of this phenomenon, the cyclic impact test of post-peak sandstone is designed, focusing on the post-peak stress state of sandstone, and exploring the post-peak dynamic response of sandstone. The post-peak sandstone specimens were prepared by a uniaxial compressor, and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment. The results show that: 1) The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure, indicating that the impact tendency of sandstone after peak decreased under lower axial pressure. On the contrary, the post-peak sandstone had strong impact tendency under higher axial pressure; 2) The higher the axial pressure, the lower the dynamic strength of the post-peak sandstone, indicating that the axial pressure promoted the failure process of the post-peak sandstone; 3) It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure; 4) Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure, and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level. The research shows that when the roadway surrounding rock was in the post-peak stress state, reducing the static stress was the key to prevent the secondary ground pressure disaster. The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment, and promote the research and exploration of post-peak mechanical properties of coal and rock.
