Abstract
Aiming at the serious problems caused by coal mine mining activities causing the rock burst accidents, this paper is based on rock mechanics and material mechanics to establish the key layer breaking by the double-key layer beam breaking structural mechanics model of a single working face and double working face under repeated mining. The theoretical calculation formula of the angle was used as the theoretical basis for the elevation angle of the pre-reloading hole of the hard roof. The rationality and reliability of the formula were verified by the physical similarity simulation experiment and the 3 Dimension Distinct Element Code numerical simulation experiment, revealing the rock formation under the influence of repeated mining. The results show that the derived key layer breaking angle formula is suitable for the theoretical calculation of the breaking angle of the key layer of a single coal seam when the repeated disturbance coefficient is λ = 1; when it is λ = 2, it is suitable for the repeated mining of the short-distance double-coal mining. The rationality and reliability of the theoretical formula of the breaking angle of the double key layer of single coal seam and double coal seam were verified by the physical similarity simulation experiment. Through the 3DEC numerical simulation results and theoretical calculation results, the W1123 working face hard top pre-cracking pressure relief drilling elevation angle was 78°. The drilling peeping method was used to verify the results. The results show that the theoretical formula of the critical layer breaking angle is well applied in engineering practice.
Highlights
When the working face of the mining is a hard top, the initial pressure step of the old roof increases sharply, resulting in a large area above the working face
Establishing broken beams over the key strata of the stope, and the mechanical model derives the formula for calculating the break angle of the key layer, and verifies the rationality and reliability of the formula through physical simulation experiments [15,16,17]
By establishing the mechanical structure model and the physical similarity simulation experiment to obtain the theory of the critical layer breaking angle, the field production practice can be better guided
Summary
When the working face of the mining is a hard top, the initial pressure step of the old roof increases sharply, resulting in a large area above the working face. Establishing broken beams over the key strata of the stope, and the mechanical model derives the formula for calculating the break angle of the key layer, and verifies the rationality and reliability of the formula through physical simulation experiments [15,16,17]. By establishing the mechanical structure model and the physical similarity simulation experiment to obtain the theory of the critical layer breaking angle, the field production practice can be better guided. The 3DEC numerical simulation was used to establish the pressure relief gradient model, which verified the rationality of the theoretical calculation results. The breaking angle of the key layer calculated by the expression is of great significance for guiding the pressure relief of the hard roof working face
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