Stability Analysis of Isolated Roof in Overlapping Goaf Based on Strength Reduction
2025
Chang Liu | Kui Zhao | Peng Zeng | Cong Gong
An isolated roof is an indispensable component of overlapping goaf. Focusing on the influence of dislocated width and width ratio on the stability of the isolated roof, this study analyzes the change rule of the safety factor of the roof supported by misaligned pillars and reveals the evolution characteristics of it by integrating numerical simulation into the strength reduction method. Firstly, with the increase of the dislocated width, the safety factor experienced three stages of sharp decrease, change from decrease to increase, and rapid increase. Secondly, the width ratio <i>λ</i> = 2 can be determined as the critical value of the safety reserve of the roof. In the interval <i>λ</i> ˂ 2, <i>F</i> decreases sharply with the increase of <i>λ</i>, but when <i>λ</i> ˃ 2, <i>F</i> decreases slowly and tends to 0. Thirdly, the overlap rate of pillars is a determinant of the type of damage but not of the safety factor of the roof. When <i>η</i> = 0, the safety factor is independent of the overlap rate. Furthermore, increasing the dislocated width can make the failure units accumulate continuously and then promote the plastic zone to expand gradually, resulting in roof collapse due to the penetration of the failure units. In this process, the tensile failure zone evolves from a single fold line to a wavy line, and the shear failure zone changes from a diagonal strip to a square strip. The study provides a new method to improve the stability of the roof, which is helpful to significantly reduce the collapse risk of overlapping goaf.
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