Study on Fracture Behavior of Directly Covered Thick Hard Roof Based on Bearing Capacity of Supports

Abstract

Mine pressure at the working face is severe due to it being directly covered by a thick hard roof. To further investigate the technology of controlling the mine pressure of a thick hard roof, the upper working face of 13,121 in Gubei mine of Huainan mining area was used as the engineering background, and similar simulation experiments, mechanical analysis, numerical simulation, and engineering applications were used to obtain the structure of a pre-cracked cut roof cut falling body, as well as establishing the mechanical model of hydraulic brace support resistance and direct covering. The results of the numerical simulation combined with the 20 m step pre-cracked top cutting showed that the cantilever length of the roof plate in the mining area was shortened by 25.61%, the stress concentration was reduced by 31.74%, and the stress level of the hydraulic brace was reduced by 26.59–28.38%, destroying the integrity of the thick hard rock body. According to the field monitoring data analysis, the working face’s initial pressure step and periodic pressure step were reduced, and the average dynamic load coefficients of the initial pressure and periodic pressure were 1.43 and 1.33, respectively, with a small dispersion of the dynamic load coefficient of the bracket. The pressure at the working face is regulated, and the chosen support equipment, in conjunction with the roof cutting scheme, can meet the thick hard roof’s support needs.