Strata Movement of Gangue Grouting Filling in Subsequent Space for Coal Mining and Analysis of Its Practical Effects

Abstract

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.

Simulation test study on filling flow law of gangue slurry in goaf

“…Reducing the ground stacking of coal gangue puts forward new requirements for the storage of coal gangue. Longterm theoretical research and practice have proved that using underground lling technology to treat coal gangue is the most reliable, thorough, and green disposal method with the lowest supervision cost at present, which not only solves the problem of coal gangue accumulation but also reduces and alleviates the surface settlement to a certain extent [9,10]. It can also inhibit the combustion of gob.…”

Research and engineering practice on space characteristics of gangue slurry filling

“…Due to different backfilling purposes, slurry backfilling differs from paste backfilling. Instead of pursuing high filling body strength, slurry backfilling primarily increases the amount of gangue filling by optimizing the slurry mix ratio and process 20 – 22 . At the same time, to reduce filling costs, the addition of binders is eliminated, but this leads to a decrease in the fine particle content of the matrix, resulting in significant differences in transport and flow performance between coal gangue slurry and traditional paste 23 – 25 .…”

Simulation test study on filling flow law of gangue slurry in goaf

“…Except for a small amount of comprehensive utilization 6 , the rest of the coal gangue is mainly processed by stacking on the ground, occupying a large amount of land resources and polluting the air, groundwater, and soil, resulting in a series of ecological and environmental problems 7 – 9 . Long-term theoretical research and practice have proved that using underground filling technology to treat coal gangue is the most reliable, thorough, and green disposal method with the lowest supervision cost at present, which not only solves the problem of coal gangue accumulation but also reduces and alleviates the surface settlement to a certain extent 10 , 11 . At present, China’s abandoned goaf is rich in space resources 12 .…”