The Characteristics of Roof Breaking and the Law of Ground Pressure Behavior in Fully Mechanized Top-coal Caving Face with Large Mining Height

In view of the characteristics of large overburden movement space, strong mining disturbance and difficult to determine the initial pressure step distance of the roof in fully mechanized top-coal caving face with large mining height, the working face 101 of a coal mine is taken as the engineering background, through theoretical analysis, numerical simulation and field measurement methods are used to analyze the roof breakage characteristics and mining pressure appearance law of fully mechanized top-coal caving face with large mining height. Firstly, the mining conditions of the working face are systematically introduced, and the influence of the fully mechanized top-coal caving face with large mining height mining conditions on the roof is analyzed. It is obtained that the direct roof collapses and forms an irregular upper direct roof and a regular lower direct roof. Large massive fine-grained sandstone above the working face are extruded into each other to form a semi-arched "rock-gangue" structure. The UDEC software is used to conduct numerical simulation to verify the initial caving step distance of the direct roof of the top coal, mudstone and fine-grained sandstone, and the broken structure of the roof of the fully mechanized top-coal caving face with large mining height under different propulsion lengths and the plastic zone and stress distribution of the roof are obtained. The research shows that: the first caving step distance of top coal is 14.52 m, the first caving step distance of mudstone is 24.06 m, and the first caving step distance of fine-grained sandstone is 47.83 m; in the special case of failure and instability of "rock-gangue" structure, the reasonable support strength P_T of the support shall be no less than 1.13 MPa to meet the requirements of roof support. Through the online monitoring of the working resistance of the hydraulic support through the support resistance monitoring system of the fully mechanized top-coal caving face 101 with large mining height, and through the analysis of the working resistance of the hydraulic support, the breaking characteristics of the roof of the fully mechanized top-coal caving face with large mining height and the regularity of the rock pressure are verified.