Controlling large deformation of deep soft rocks

During deep coal mining, roadway surrounding rocks are subjected to high in situ stress and intense mining disturbances, making them susceptible to meter-scale large deformation. With increasing mining depth, the in situ stress of deep surrounding rocks continuously increases, and the manifestation of mining pressure becomes increasingly intense. This challenge significantly impedes the safe and efficient extraction of deep coal resources. To address this challenge, based on the engineering geological conditions and mining characteristics of deep coal mines under dynamic pressure, this study proposes a novel stress compensation and pressure relief (SCPR) synergetic control technology. This approach integrates the "constant-resistance and large deformation (CRLD) anchor cable + grouting" technology with the deep-and-shallow hole roof-cutting blasting (DSH–RCB) control technology. Taking the kilometer-deep coal mine of Huainan in China as an engineering case, theoretical analysis and model testing were conducted to illustrate the control mechanism. The results demonstrate that the SCPR control technology enables multi-scale synergetic regulation of strength compensation, stress compensation, and pressure-relief compensation for the roadway surrounding rocks. It effectively reduces the influence range and intensity of dynamic pressure, and significantly optimizes the stress environment of the surrounding rocks. Furthermore, field test results indicate that, compared with conventional control technologies, the SCPR technology reduces the deformation of surrounding rocks by 75%, decreases the advanced influence range of mining pressure by 33%, lowers the pressure borne by the support by 28.7%, and shortens the periodic weighting step by 37.6%. The results of this study present a new technical pathway for controlling large deformation in kilometer-deep soft rock roadways subjected to medium-to-strong dynamic pressure.