Developing a New Bursting Liability Index Based on Energy Evolution for Coal under Different Loading Rates

The risk of a coal burst rises with the excavation depth and other mining-related activities. These devastating coal burst activities are a major concern during deep coal mining. During such activities, the loading rate is a major cause of damage. Different indexes, including the elastic strain modulus index (W_et), bursting energy index (K_e), dynamic failure time index (D_T), and compressive strength index (R_c), are used for coal bursting intensity; however, the loading rate and damage factors are not included in these indexes. In this study, a new coal bursting liability index called the elastic modulus damage index (EMDI) was developed using rock damage variables and the elastic strain modulus index, and is based on energy evolution characteristics under different loading rates. The results of this new index were compared with the existing indexes, and their range was proposed to evaluate coal bursting liability. The EDMI shows a positive polynomial second order degree relationship with W_et and K_e, having a determination factor of 0.99, while D_T shows a negative polynomial second order degree relationship with a determination factor of 0.94. The EDMI and R_c show a positive power relationship having a determination factor of 0.99. The relationships with other indexes revealed that the EDMI can be effectively used in evaluating the coal bursting liabilities in different stress environments.