Study on Deformation Characteristics of Surrounding Rock of Roadway with Coal–Rock Interface

Surrounding rock of roadway with a coal–rock interface is a common form in coal mines. In order to determine deformation characteristics and obtain the control principle of roadways with a coal–rock interface, the interface between the roof and coal seam was added to simulate the weak cohesion between the stratum. In this model, the interface shear stiffness was considered to be one of the key factors affecting horizontal inward movement of the roadway sidewalls. The deformation of the roadway with or without coal–rock interface under different burial depths was analyzed. Then, the shear stiffness of the interface element was changed to study the influence of shear stiffness on roadway deformation. At the same time, the characteristics of discontinuous deformation caused by the coal–rock interface at different positions in the roadway were studied. The results show that the roadway sidewall appeared to bulge in the middle and there is no dislocation and a small deformation in the contact position of the roadway sidewall with the roof and the floor when there is no interface between the stratum of the roadway. When there is an interface, the sidewall of the roadway is extruded as a whole, the slip and dislocation between the coal sidewall and the roof were obvious, and the maximum deformation of the sidewall is 1.68 times that of the roadway without an interface. When the shear stiffness of the interface is low, the deformation and the range of the plastic zone of roadway are large, with a large deformation at the upper part of the roadway sidewall, and a small deformation at the lower part of the roadway sidewall. The deformation of sidewall at the interface position decreases gradually with the increase of the interface shear stiffness, approaching the shape without the interface. When the coal–rock interface is at the sidewall of the roadway, the deformation of the rock and coal body at the interface is discontinuous, with slip and dislocation. The greater the proportion of rock height in the roadway sidewall, the greater the rock deformation. On the contrary, the coal deformation increases. It is more reasonable to simulate the deformation of roadways by adding a coal–rock interface, and the results are closer to the actual situation.