Study on the fracture characteristics of overlying rock strata under different mining face widths

To evaluate the influence of mining face width on the fracture characteristics of overlying rock strata, a mechanical model of overlying rock strata before fracture is established based on Winkler's elastic foundation hypothesis. This model incorporates Timoshenko's solution to calculate the variation of bending moment and shear force under different foundation conditions. The physical experimental results reported in relevant literature have also verified that the overlying rock strata are fractured with trapezoidal structure. Subsequently, the relevant parameters of this trapezoidal spatial structure about overlying rock strata before and after periodic roof weighting are analyzed in detail, and the calculation results show that the height of trapezoidal spatial structure is directly affected by the width of mining face, and the fractured form of rock layers changes from a horizontal "O-X" structure to a vertical "O-X" structure from the bottom up. Afterwards, the stability verification of inferior key layers is conducted following the trapezoidal spatial structure. Based on elastic thin plate theory, the mine pressure characteristics are analyzed, and the relationship curve of hanging length and hanging width of any rock layer in the overlying rock strata is obtained. Finally, the influence analysis of mining face width on type selection of hydraulic support is demonstrated based on the Panels 1302 and 1305 belonging to Zhaozhuang No.2 underground mine, and the on-site engineering application effect is significant.