Model of overburden pressure arch in mining areas considering thick-hard rock layer and application

The mining pressure arch model and the thick-hard rock layer beam structure model are important spatial structural models for analyzing mining pressure and rock layer control. The interaction between these two models affects the movement of overlying rock and the characteristics of mining pressure manifestation in working face under mining disturbance. Based on this, this paper combines the theory of pressure arch and the theory of beam structure in thick-hard rock layers, and constructs a unified theoretical model of thick-hard rock layers-pressure arches based on the relationship between the fracture of thick-hard rock layers and the development height of pressure arches. At the same time, based on the thick-hard rock layers-pressure arch model, the influence of mining conditions and thick-hard rock layers on the development of overlying rock fracture and mining pressure manifestation is analyzed. A prediction calculation model for the weighting of longwall face is further constructed. A calculation method for the development range of overlying rock fracture under different influential factors are obtained. The research results indicate that because of the delayed fracture of thick-hard rock layers and asymmetric development of the pressure arch caused by stress concentration on the hanging roof, their linkage fracture contributes to the occurrence of stronger mining pressure. The initial fracture distance of the thick-hard rock layers linearly increases with the rise of the rock layers’ thickness, and the failure gradually transfers from shear to tensile. The initial fracture distance of the thick-hard rock layers increases with the increase of advancing speed. However, the effect on the fracture distance will shrink after the advancing speed expands to an extent. When there exist multi-strata of thick-hard rock layers, the initial fracture distance of the lower thick-hard rock layers shows a non-linear decreasing trend. Finally, the model proposed in this paper is used to calculate the weighting distance of the 12401-longwall face in Shangwan Coalmine. When the advancing speed is slower, the average period of weighting distance is 11.76 m, and when the advancing speed is faster, the average period of weighting distance is 18.33 m, which is basically consistent with the field measurement results.