Research on surrounding rock control technology based on directional presplitting roof cutting and pressure relief in fully mechanized withdrawal roadways

Abstract

Surrounding rock control of a withdrawal roadway (WR) in longwall mining is essential for ensuring equipment safety and completing equipment withdrawal. Under deep and complex geomechanical conditions, conventional support systems often fail to withstand the strong disturbance induced by hydraulic support (HS) withdrawal during the withdrawal stage (WS). In this study, the instability mechanism of the WR and the corresponding control technology were investigated through theoretical analysis, numerical simulation, and a physical model experiment monitored using digital image correlation (DIC). Based on the masonry-beam (MB) mechanical model of the key roof block, WR instability is attributed to the disruption of the original moment equilibrium of key block-B as HS restraint decreases during the WS, which drives block-B from a stable state to rotational instability. Therefore, effective regulation of the rotational motion of block-B is identified as the key requirement for maintaining surrounding rock stability. To control this failure mode, a coupled control strategy integrating directional pre-splitting roof cutting and pressure relief (DP-RCPR) and Negative Poisson’s Ratio(NPR) cable active support (NPRC-AS) is proposed. The experimental and numerical results indicate that directional pre-splitting cuts off the lateral mechanical linkage between adjacent key blocks and promotes stable contact between the main roof in the goaf and the caved gangue, so that the goaf evolves from a load source into a load-bearing structure. In addition, the NPR cables, characterized by constant resistance and large deformation capacity, provide high-resistance support for both the immediate roof and the main roof, thereby enhancing the integrity of the roof-bearing system. Field implementation demonstrates that the proposed core technologies effectively control WR deformation. The developed approach provides theoretical support and technical guidance for HS retreat under deep dynamic ground-pressure conditions.

Keywords

mining face withdrawal roadway / roof stability / roof cutting and pressure relief / surrounding rock control

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