Study on the Influence of Grouting Treatment on the Movement and Deformation of Surface in Longwall Coal Mining Goaf Areas

The grouting treatment of the old goaf in a coal mine is an essential measure to ensure the safety of the road above it. A novel calculation model is proposed to more accurately determine the appropriate treatment range for the goaf on the road. Compared with traditional mining subsidence calculation models, this new model demonstrates improved fitting to the observed deformation in experimental studies. The deformation of the grouted area is caused by the residual deformation of the untreated goaf areas, and the deformation of the treated area is different from that of the area above the coal wall in the mining stage, which is made by the grouting reinforcement body after grouting treatment. The walking rule (walking probability) of the random medium theoretical walking model is enhanced in this paper to describe this distinction, and a calculation model suitable for quantitative analysis of surface residual deformation in road goaf after grouting reinforcement is established. The standard recommended method, the probability integral method, and a newly derived improved calculation formula are compared in this study. The treatment width predicted by the standard recommended method is the widest, reaching 182 m. The probability integral method predicts a narrower width of 139 m; while the improved calculation formula predicts the narrowest width of 124 m. Compared to the former two, the improved calculation formula not only considers factors such as the depth of the goaf, the overlying strata lithology but also the residual deformation and the grouting reinforcement body. An innovative and effective method for calculating the surface deformation of goaf areas after grouting treatment is developed, thereby offering a basis for designing more precise goaf treatment schemes.