Wu Cai

Fault is a common geological structure that has been revealed in the process of underground coal excavation and mining. The nature of its discontinuous structure controls the deformation, damage, and mechanics of the coal or rock mass. The interaction between this discontinuous structure and mining activities is a key factor that dominates fault reactivation and the coal burst it can induce. This paper first summarizes investigations into the relationships between coal mining layouts and fault occurrences, along with relevant conceptual models for fault reactivation. Subsequently, it proposes mechanisms of fault reactivation and its induced coal burst based on the superposition of static and dynamic stresses, which include two kinds of fault reactivations from: mining-induced quasi-static stress (FRMSS)-dominated and seismic-based dynamic stress (FRSDS)-dominated. These two kinds of fault reactivations are then validated by the results of experimental investigations, numerical modeling, and in situ microseismic monitoring. On this basis, monitoring methods and prevention strategies for fault-induced coal burst are discussed and recommended. The results show that fault-induced coal burst is triggered by the superposition of high static stress in the fault pillar and dynamic stress from fault reactivation. High static stress comes from the interaction of the fault and the roof structure, and dynamic stress can be ascribed to FRMSS and FRSDS. The results in this paper could be of great significance in guiding the monitoring and prevention of fault-induced coal bursts.

Rock bursts have become one of the most severe risks in underground coal mining and its early warning is an important component in the safety management. Microseismic (MS) monitoring is considered potentially as a powerful tool for the early warning of rock burst. In this study, an MS multi-parameter index system was established and the critical values of each index were estimated based on the normalized multi-information warning model of coal-rock dynamic failure. This index system includes bursting strain energy (BSE) index, time-space-magnitude independent information (TSMII) indices and time-space-magnitude compound information (TSMCI) indices. On the basis of this multi-parameter index system, a comprehensive analysis was conducted via introducing the R-value scoring method to calculate the weights of each index. To calibrate the multi-parameter index system and the associated comprehensive analysis, the weights of each index were first confirmed using historical MS data occurred in LW 402102 of Hujiahe Coal Mine (China) over a period of four months. This calibrated comprehensive analysis of MS multi-parameter index system was then applied to pre-warn the occurrence of a subsequent rock burst incident in LW 402103. The results demonstrate that this multi-parameter index system combined with the comprehensive analysis are capable of quantitatively pre-warning rock burst risk. Keywords: Rock burst, Microseismic (MS) monitoring, Multi-parameter indices, Comprehensive early warning