Strain characteristics and energy dissipation laws of gas-bearing coal during impact fracture process

Abstract

To reveal fracture mechanism of gas-bearing coal subjected to complex geology environment, the impact dynamics experiments were conducted to study energy characteristics based on split Hopkinson pressure bar (SHPB) system. The incident, reflected and transmission strain were collected to calculate various energy. It was found reflected strain was always larger than transmission strain. Therefore, the reflected energy was generally higher than transmission energy under different loading conditions, but they were smaller than incident energy. With time evolution, both elastic deformation and dissipative energy experienced slow increase, rapid increase, peak point and decrease stage regardless of loading conditions. Before macro failure, micro-meso fractures had changed drasticly, which also involved intense energy conversion. So dissipative energy peak was earlier than that of elastic deformation energy. Due to pre-damage of static load and weakening effects of gas, the dissipative energy decreased with their increases (static load from 2.00 to 9.00 MPa and gas pressure from 0.25 to 1.50 MPa) during impact fracture process. However, at high confining pressure and dynamic load environment, the impact failure of gas-bearing coal exhausted massive energy. These energy characteristics will provide guidances to prevent and control disaster during coal mining and coal seam gas (CSG) exploitation in deep area.