Experimental study on roadway backfill mining of paste-like material

Roadway backfilling mining is vital for ensuring the safety of surface buildings while mining coal underneath buildings, railways, and water bodies. The technique and backfilling material, however, need to be optimized to ensure the long-term safety of the project and surface structures. Using a mine as the engineering background, reasonable strength, an optimal ratio of backfilling materials was determined by using numerical simulation and indoor testing. Displacement characteristics of the surface were analyzed after the roadway backfilling mining technology was completed using similar simulations. The research results showed that the overburden strata could be effectively controlled when the strength of the backfill material is 0.6 to 0.8 times that of the coal. The optimal ratio of the paste-like material is 80% fly ash, 5% mineral powder, 15% quicklime, 4% gypsum (external doping), 1% activator A1, and 0.02% expansion agent. The subsidence of the overburden strata in a similar model was characterized by two rapid sinking stages, with a final surface maximum horizontal deformation value of 0.011 mm/m and a maximum curvature value of 0.043. After performing an industrial test on a working face, the maximum subsidence of the surface of the filling area was 289 mm, indicating that the surface structures were within the range of I level damage.