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.

Failure characteristics of thick hard roof stratum under hydraulic pre-splitting and its application in a coal mine, Dongsheng mining area

“…However, the effect of complicated geological conditions such as the thick hard roof and top coal on the mining operation has somewhat restricted the successful implementation of this technique (Gu et al, 2022). Mine disasters induced by the excavation of thick coal seams tend to occur due to the presence of a thick hard roof with high strength and elasticity strain energy overlying the excavation of coal seams (Li et al, 2023;Sepehri et al, 2020). As a working face continues to advance, roof strata without naturally caving form a large-scale suspended roof, resulting in a vacant area without caved rock blocks behind the coalface.…”

Research on the Deformation Law and Stress Distribution Characteristics of Overburden under the Influence of Multiple Faults

“…In order to meet the needs of national construction and improve coal output, it is necessary to study coal mining under complex geological conditions. Many scholars have conducted research in different directions, such as deep coal mining [1][2][3], coal mining in fault-affected areas [4][5][6], underground mining of thin coal seams [7][8][9], and mining under hard roof conditions [10][11][12]. In these mining conditions, the fault is exceptional.…”

Study on the Spatiotemporal Dynamic Evolution Law of a Deep Thick Hard Roof and Coal Seam

“…Thick and hard roof slabs are distributed in more than half of China's mining areas, and the occurrence conditions of coal seams are relatively complex. Today, with the widespread use of fully mechanized mining technology, nearly 40% of fully mechanized mining faces have experienced the phenomenon of thick and hard roof falling violently for the first time [8][9][10].…”