A STUDY ON THE LAW OF OVERLYING STRATA MIGRATION AND SEPARATION SPACE EVOLUTION UNDER HARD AND THICK STRATA IN UNDERGROUND COAL MINING BY SIMILAR SIMULATION

Abstract

The breaking of hard and thick key layers can easily cause dynamic disasters, such as rock burst and mine seismicity, and seriously threaten safe mining. To analyze the characteristics of overburden breakage and law of evolution of separation cracks under mining of hard and thick rock stratum, and to further reveal the process of the occurrence of dynamic disaster, the fracture characteristics of overlying strata during mining were analyzed via similar simulation in this study. The characteristics of surface movement and deformation before and after the breaking of hard and thick strata were then discussed based on the law of overlying rock displacement. Finally, the development law of separation fissure in hard and thick rock stratum was revealed. Results show that the key stages of overlying strata movement during mining are immediate main roof breaking; main roof cycle breaking; and hard and thick rock breaking. The hard and thick strata, which are the key strata, bear the weight of the overlying strata with small subsidence before breakage. Development of the separated stratum stops at the bottom of the hard and thick strata and maintains an unclosed state for a long time, providing the formation space for the accumulation of gas and water in the separated bed. When the hard and thick rock is broken, the subsidence of the overlying strata increases dramatically, and the separated stratum is closed rapidly, inducing gas outburst, water inrush, dramatic surface subsidence, and other disasters in the working face easily. The outcomes of this study are significant to the safe mining of working face under similar geological conditions.