Coordinated Deformation Mechanism of the Top Coal and Filling Body of Gob-Side Entry Retaining in a Fully Mechanized Caving Face

Abstract

When gob-side entry retaining technology is used in a fully mechanized caving face, the load-bearing structure of the filling body and top coal often cannot meet the series of dynamic deformation problems caused by the roof breaking and turning. To solve this problem, the mine pressure model and the load-bearing structure diagram of gob-side entry retaining in a fully mechanized caving face are established. Based on the elastic modulus of the filling body and top coal, the interaction relationship between the top coal and the filling body is derived. Through numerical simulations, the deformation and stress laws between the top coal and the filling body with different physical and mechanical properties are analyzed. Finally, a similar simulation test is used to analyze the stability of the gob-side entry retaining under different top coal conditions. The results show that the deformation of the top coal increases with an increase in the elastic modulus of the filling body, and the vertical deformation of the filling body increases with an increase in the elastic modulus of the top coal. The elastic modulus of the filling body should be 4.3–5.5 GPa based on the theoretical calculation. The vertical stress of the filling body increases with an increase in the elastic modulus of the top coal. The higher the stiffness and strength of the top coal, the better the transmission of the force. The vertical stress on the top coal increases with an increase in the elastic modulus of the filling body, and the subsidence of the top coal decreases with an increase in the elastic modulus of the filling body. If the elastic modulus of the filling body is too small, it is easy for it to deform itself. When using gob-side entry retaining technology in a fully mechanized caving face, the stiffness and strength of the filling body should not be as large as possible. If the filling body is too soft, the stiffness and strength of the filling body should be properly reduced to prevent the top coal from breaking, resulting in poor contact with the filling body. When the top coal is too hard, the stiffness and strength of the filling body should be appropriately increased to prevent the filling body from cracking and slipping. At the same time, it was verified that the filler with an elastic modulus of 5 GPa can meet the stability requirements of a fully mechanized caving face 8103.