Investigation of the Evolution Characteristic of Abutment Pressure during the Longwall Retreat Mining Process: A Case Study Using Field Tests and Numerical Simulation Method

Mining-induced disturbance to stress fields can lead to many engineering disasters such as rock bursts, roadway collapses, and coal and gas outbursts. The evolution characteristic of abutment pressure during the mining process is of great significance for prevention of engineering disasters. Based on a case study of No.12526E Panel in Xieqiao coalmine of Huainan mining area in China, this paper investigated the evolution characteristic of abutment pressure during the retreat mining process. A field measurement was performed using three-dimensional (3D) pressure sensor, and the abutment pressure was continuously monitored during the mining process. The monitoring results indicate that the abutment pressure curve can be divided into strong interference area and weak interference area. Further, the evolution characteristics of abutment pressure during the retreat mining process were simulated using a 3D discrete-element program. Periodic caving characteristics of rock strata were obtained, and the major causes of stress concentration and the bearing stress inflection point were analyzed. With the periodic caving of the overlying strata, the stress inflection point appears, and fracture cracks are generated and hinder stress recovery. Finally, the detailed dynamic evolution process of the abutment pressure as well as the deformation and caving characteristics of the overlying strata of the No.12526E Panel were analyzed. The coal and rock near the mined-out area undergo a sharp stress concentration and reduction, which would lead to damage to the rock mass near the mined-out area.