Study on Surrounding Rock Movement of Fully Mechanized Top-Coal Caving with Strong Impact Under Thick-Hard Strata

In view of the serious damage of roadway and the severe roof weighting of the 3302 working face, microseismic monitoring and surrounding rock displacement monitoring system were used to conduct on-line in-situ monitoring. In this paper, the energy distribution and microseismic event distribution of stope in the primary impact stage and the “square” stage (The working face is pushed to the stage where the strike length of the mined-out area is equal to the dip length, i.e., the stage of “square” of the working face.) are studied. On this basis, the deformation and failure law of the roadways is analyzed. Furthermore, the breaking regularity of multiple thick and hard strata with fully mechanized top-coal caving is obtained. Due to the high span of the fully mechanized caving face, the failure region of the overlying strata expands. As the fracture of the 3rd hard layer, the rotation and deformation of the upper rocks expand. With the periodic fracture of the 3rd hard layer, the hanging area of the 6th hard rock layer increases, which finally leads to its fracture. The weighting of stope is severe during the “square” stage, which is recorded through field monitoring. Through the preliminary analysis, it is concluded that the fracture of the 3rd and the 6th hard stratum contribute to the severe weighting during the “squire” stage, which is easy to induce rock burst. Over the primary impact period, the occurrence of seismic events is frequent and the ground pressure is strong. The maximum approach between two sides of roadway is about 750 mm, and that between the top and bottom is 1300 mm. The periodic weighting of three different “source points” is analyzed by numerical simulation. It is found that the peak value of leading abutment pressure in “square” stage is 82.09 MPa. Finally, the high risk zone of rock burst is obtained, and the predictable “pressure relief zone” is determined, which provides an important reference value for the prevention of rock burst in multi-layer thick and hard rock strata in a super kilometer deep well.