Fault-induced coal bursts in underground coal mines: Experimental and numerical investigations

The fault structure in coal mines is one of the major factors that could cause coal bursts—a dynamic disaster in underground mining. Investigating the formation of normal and reverse fault structures serves as a crucial pathway for distinguishing between different types of coal bursts. To understand the characteristics of fault slip and coal bursts induced by fault instability in underground coal mines, a series of experiments were conducted to examine the influence of fault dip angle on fault slip behavior. Furthermore, the formation mechanisms of normal and reverse faults were explored. During the experiments, the fault slip displacement, rock failure patterns, and stress evolution along the fault surface were observed. Additionally, a numerical model of fault slip was established with different fault dip angles, and the fault slip proneness was investigated under both in situ normal fault and in situ reverse fault conditions. The fault relative displacement with different dip angles under horizontal force was calculated using a point-by-point integration calculation method, while the stress criterion and geometric constraints governing fault formation were theoretically determined. The different fault slip behaviors can be recognized with fault dip angles, and fault formation mechanisms were subdivided. According to the influence of fault dip angle on the fault slip behavior, the slip patterns are divided into three categories using the key angles of 30° and 55° as demarcation points. By incorporating an additional key angle of 45°, the three patterns are then refined into four types of fault formation mechanisms. Finally, this study analyzed the coal bursts induced by each of these four fault formation types, including reverse and normal faults under in situ reverse fault conditions, and normal and reverse faults under in situ normal fault conditions.