Analysis of Surface Cracking and Fracture Behavior of a Single Thick Main Roof Based on Similar Model Experiments in Western Coal Mine, China

Surface subsidence over coal mines in western China is serious. Collapse pits, step subsidence, surface cracks, among others occur during coal mining. Based on data of surface subsidence in western mining area, this study analyzed the control of key strata on surface subsidence. The breaking mode of the main roof with different thicknesses was discussed based on self-designed simulation test device for the initial breaking of main roof. Through physical experiments, two types of breaking models of the main roof, namely horizontal X type and vertical X type, were obtained. With the increase in the thickness of the roof, the roof was more prone to sliding instability. Based on Reissner's thick plate theory, mechanical model of the initial breaking of the main roof was established, and the parameters such as thickness, step distance, Poisson's ratio, and burial depth were introduced. Through theoretical analysis, the fracture critical condition and breaking mode partition of main roof were obtained. According to the characteristics of surface subsidence of shallow coal seam, the mechanism of strata movement controlled by layered hydraulic fracturing technology was analyzed in the western coal mines of China. This study provides a theoretical reference for the prevention of main roof sliding instability and the control of surface subsidence.

Automated summary

Surface subsidence over coal mines in western China is a serious issue, with various problems such as collapse pits, step subsidence, and surface cracks occurring during coal mining. This study analyzed the control of key strata on surface subsidence based on data from the western mining area and discussed the breaking mode of the main roof with different thicknesses through physical experiments. By establishing a mechanical model and introducing parameters such as thickness and burial depth, the study obtained fracture critical conditions and breaking mode partition for the main roof. The analysis also examined the mechanism of strata movement controlled by layered hydraulic fracturing technology in western coal mines, providing theoretical reference for preventing main roof sliding instability and controlling surface subsidence.