Research on mechanism and control technique of floor heave in deep soft rock roadway at Banji Coal Mine

Aiming at the severe floor heave occurring at the machine head section of the belt conveyor downhill roadway in the 1105 mining area of Banji Coal Mine, Bozhou, Anhui, a systematic investigation was conducted using mechanism analysis, numerical simulation, and on-site industrial testing to elucidate the multifactorial mechanism and control technique of floor heave in deep soft rock roadways. The dominant factors contributing to roadway floor heave were identified as high horizontal tectonic stress, weak floor lithology, high water content in the floor strata, and deficiencies in the original support system. Subsequently, the loosening zone of the roadway floor was detected, and the development characteristics of floor plastic deformation and deformation concentration were analyzed in detail. On this basis, the reasonable effective depth for grouting reinforcement was determined. Accordingly, an integrated floor heave control technique combining deep-hole high-pressure grouting and drainage was proposed to reinforce and strengthen the roadway structure. A numerical model was then established to comparatively analyze roadway deformation over a three-month period under conditions with and without reinforcement. The results indicate that the overall stress state of the surrounding rock was significantly improved after reinforcement, leading to effective control of floor heave deformation, while deformation of the roof and sidewalls was simultaneously mitigated. Furthermore, on-site monitoring results demonstrate that 30 d after grouting, floor subsidence, inwardconvergence of the two sides, and floor heave of the roadway ceased completely, and the deformation gradually stabilized. These findings confirm that the proposed floor heave control technique can effectively suppress deformation of the roadway surrounding rock and ensure safe and stable operation.