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

Fracture of the hard and thick key layer can easily cause dynamic disasters, such as the rock burst and mine seismicity, which
seriously threatens the safety of underground coal mining. To
analyze the characteristics of overlying strata fracture and law
of evolution of separation fissures under hard and thick strata in
underground coal mining, and further reveal the process of the
occurrence of dynamic disasters, the fracture characteristics of
overlying strata during underground coal mining were analyzed
via similar simulation in this study. The characteristics of surface
movement and deformation before and after the fracture of hard
and thick strata were then discussed based on the law of overlying
rock displacement. Finally, the development law of separation fissures under the hard and thick strata was revealed. Results show
that the key stages of overlying strata movement during underground coal mining are immediate roof fracture, main roof fracture; main roof cycle fracture, and hard and thick rock fracture,
respectively. Before the hard and thick strata are fractured, as the
key layer, bearing the weight of the overlying strata and the overburden strata subsidence is small. The developmental height of the
separated stratum stops at the bottom of the hard and thick strata, and the separated stratum stays in an unclosed state for a long
time, which provides the incubation space for the accumulation
of gas and water in the strata. After the hard and thick strata are
fractured, the subsidence of the overlying strata increases dramatically, and the separated stratum is closed rapidly, inducing gas
outburst, water inrush, dramatically surface subsidence, and other
disasters in the working face. The research results of this study are
of considerable significance to the safe mining of working face
under similar geological conditions.