One equivalent mining height model for predicting the compression-consolidation-creep-diagenesis of compacted gangue backfill body——A case study on double wide-strip mining with gangue backfill

Abstract

Abstract Taking the double wide-strip mine gangue backfilling work face of 1101 and 1102 in the Tingnan Coal Mine as the background, this study utilizes theoretical analysis, numerical simulation, laboratory experiments, and engineering practices to investigate the complete process of compression-consolidation-creep-diagenesis of the compacted gangue backfill body, the equivalent mining height model, and the surface subsidence characteristics. The results: The maximum control roof distance in the gangue backfilling work face=Tip-to-face distance + Cutting depth + Roof beam length + Post-support gap. The advance subsidence amount of roof is equal to the maximum control roof distance multiplied by the sine value of the roof inclination angle. The height of available backfill space behind the support is equal to the mining height minus the roof advance subsidence, the unfilled height under roof, and the amount of floor heave behind the support. The compacted gangue body undergoes four stages of compression-consolidation-creep- diagenesis within the available filling height, with their respective compressibility rates as follows: skeleton adjustment stage (7.42%), slow compression stage (12.81%), consolidation settlement stage (13.15%), and creep diagenesis stage (25.53%). The equivalent mining heights corresponding to the four stages are 0.94m, 1.10m, 1.11m, and 1.48m, respectively. By comparing the predictions from probability integral method, numerical simulations, and subsidence observations, it is evident that the surface subsidence curves of the 1101 and 1102 working faces, along the strike main section, exhibit a "bowl" shape, with a gentle slope in the first two stages and a steep slope in the latter two stages. ht=Lmax×sinθ The subsidence curves of the 1101 and 1102 working faces, along the dip main section, show a "bowl" shape in the first two stages, and a "W" shape in the latter two stages.