Movement Law of Overlying Strata and Abutment Pressure Redistribution Characteristic Based on Rigid Block

Abstract

Abstract Roof movement induced by coal excavation is the immediate cause of rock pressure redistribution and strata behavior. The rigid block in PFC3D was used to generate a multijointed rock mass, and the PFC3D–FLAC3D coupling model was used to study the movement law of the highly developed structural plane of the overlying strata. Strata movement and abutment pressure redistribution characteristics were obtained. The numerical simulation results showed that the multijointed rock mass model reproduced a rock mass with highly developed structural planes. After coal seam mining, the immediate roof caved and filled the goaf, forming an irregular and regular caved zone. The immediate roof shear slipped along the coal wall. The fracture of the basic roof formed a fractured zone, and the maximum height of the fractured zone first increased and then decreased, exhibiting continuous slow subsidence. The fluctuation of the front abutment pressure was reduced, and the abutment pressure in the goaf jumps was discontinuous. The abutment pressure in the goaf was high in the middle and low on both sides. After the initial fracture of the basic roof, the stress concentration of some rock blocks in the goaf exceeded the in-situ stress, and the average abutment pressure increased with the working face advancing length. With the coal wall of the working face gradually moving away from the goaf, the abutment pressure of the goaf first increased and then remained unchanged; the porosity first decreased sharply and then declined slowly; the coordination number of particles rose sharply and then increased slowly, indicating that the goaf gradually stabilized. Similar simulation results indicated that the variation law of abutment pressure, caving characteristics of the immediate roof, and continuous slow subsidence of the basic roof were the same as those of the numerical simulation.