Solid waste filling and roadway retaining can effectively control surface subsidence and alleviate solid waste accumulation pollution. In order to effectively evaluate the advantages of solid waste filling in deformation control of overlying strata and surrounding rock of retained roadways, this study used theoretical analysis and numerical simulation methods to analyze the factors affecting surface subsidence, as well as the deformation characteristics of surrounding rocks and retaining tunnels during backfill mining. By calculating the influence of factors such as the foundation coefficient and the filling rate on the subsidence of the roof, it is concluded that the filling rate is the main controlling factor affecting the subsidence of the roof. Through simulation and comprehensive analysis of the impact of different filling rates on overlying rock migration, it was found that when the filling rates are 70 % and 80 %, it can effectively control the subsidence of overlying rock in the mining area. By simulating the effects of these two filling rate conditions on the deformation of surrounding rock within the retained roadway zone, the results show that the optimal filling rate that can effectively control the subsidence of the overlying rock and improve the stability of the retained roadway is 80 %.

Coal mine backfilling mining controls the movement of overlying rock and surface subsidence by backfilling the fractured rock mass into the goaf. The compaction mechanical performance of the fractured rock is the key to the effectiveness of overlying rock control. In order to optimize the control effect of crushed gangue overlying rock, this article focuses on the regulating effect of gangue particle size grading on mechanical properties. Through research on the physical properties of gangue and natural graded gangue compaction experiments, the porosity of gangue crushing and the process of gangue crushing are analyzed. It is shown that the gangue material has good load-bearing performance in terms of physical structure, and the elastic modulus has an absolute effect on the compression characteristics of gangue particles. Through storage analysis of the natural grading experiment phenomenon, it was found that the alarm height for gangue not to be blocked is 20m. Through laboratory experiments, the compression characteristics of group B samples were analyzed, and it was found that the particles showed a trend of first increasing and then decreasing under the coupling effect of particle size and particles of different sizes. Through the analysis of particle strain energy density and breakage energy, it is concluded that the strain energy density of the sample from high to low is B1, B2, B6, A5, B5, B4, and the breakage energy consumed to reach the sample broken state from low to high is A5, B6, B5, B4, B3, B2, B1, so the B6 group samples have the best economic benefits. Through analysis from the perspective of filling rate, it was found that the B6 group of samples has the best control effect on the overlying rock. Thus providing suggestions for optimizing the efficiency and effectiveness of backfill mining.