Research on optimum design of parameters of fully mechanized mining face under goaf in soft rock mine

With the mining of the Ⅱ₃ coal seam under goaf in soft rock of Lingdong coal mine as the background, three factors such as the length of the working face, the width of the sectional coal pillar and the mining height are selected for orthogonal test design, and the FLAC^3D numerical software is used to simulate the working face under different combinations of factors.The damage of the rock, analyze the influence of each factor on the damage of the overburden of the working face.The test results show that the significant order of the influence of various factors on the roof failure height of Ⅱ₃ coal seam is:height of mining> length of working face> section pillar width.Based on the analysis of the numerical simulation results, combining with the influence curves of various factors on the height of the water-conducting fissure zone, and following the basic principles of safe and efficient production of coal mines, the reasonable size combination of Ⅱ₃ coal seam working face is determined as the length of the working face is 250 m, and the width of the sectional coal pillar is 25 m and the mining height is 5 m, and comparing with the simulation results of medium-hard rock formation, reflecting the damage degree of soft rock formation in the simulation.