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There is a huge amount of solid waste generated in coal resource exploitation and utilization, leading to effects on the environment and hindering sustainable development. Aiming at the difficulty of disposal of coal-based solid waste from high-yield, high-efficiency mines, this research proposed a technique of gangue grouting filling in subsequent space (GGFSS) for coal mining and explored the movement of key strata backfilled using GGFSS technique and surface deformation characteristics using theoretical analysis and a field measurement method. The results indicate that the equivalent backfilled ratio (EBR) when using GGFSS is defined as the ratio of the grouting volume to available void volume, which is mainly affected by bed separation void volume, grouting volume, and the void volume of the caving zone. Using an EBR ground control mechanical model, the changes in the displacement and bending moment of key strata with the variation of the EBR were investigated. The critical EBR for the rupture of key strata was determined to be 74.44%. On this basis, the calculation methods of equivalent mining height (EMH) and the subsidence factor of GGFSS were proposed and then a surface deformation prediction model of GGFSS was established based on the principle of the probability integration method. The predictions implied that, at an EBR greater than 75%, the surface deformation could be significantly reduced. Engineering applications verified the effect of GGFSS on the control of ground movement. In-situ measurements of concentration, density, and particle size of the filling body were all close to the those designed values: the GGFSS technique shows longer grouting duration and a larger amount of grouting and its filling body can support impervious key strata above the working face in a mine, significantly decreasing surface subsidence. [ABSTRACT FROM AUTHOR]

For investigating perceptual stress characteristics of Functional Cemented Backfilling Materials (FCBM) in coal mines, we prepared functional specimens based on Cemented Backfilling Materials (CBM) with the perceptual stress ability, and clarified their conductive mechanism, perceptual mechanism, and possible engineering applications. Using mechanical tests and the network parallel dynamic method, the mechanical and electrical properties of the prepared materials and the perceptual characteristics under mechanical–electric coupling conditions were analyzed in depth. The test results demonstrate that the deformation of FCBMs obey standard stress–strain rules, while the conductive phase addition can deteriorate their mechanical properties and simultaneously enhance the electrical conductivity of materials. Through fitting, the percolation threshold was determined to be 9.85%. Before the failure, the spatial distribution of the apparent resistivity in the materials was shown to follow the X-shaped radial pattern; after the failure, the material apparent resistivity obeys different distribution rules at various stages. The apparent resistivity of FCBM is negatively correlated with the strain value at the elastic and plastic stages and positively correlated with it at the failure stage. When the graphite content exceeds the percolation threshold, the materials exhibit a favorable perceptual functionality at the elastic stage. [ABSTRACT FROM AUTHOR]