Abstract
The coal mining technology of fully mechanized solid filling is an efficient and green mining method that integrates “sediment reduction” and “emission reduction.” However, the discharge of wasted gangue and surface subsidence are controlled by the amount of wasted gangue used in filling mining and the compaction rate of gangue filled into a goaf, respectively. To increase the consumption of wasted gangue and reduce surface subsidence, mixed gangue composed of equal-quality washed gangue and crushed gangue is proposed as a raw material for solid filling on the basis of gradation theory. Next, a screening experiment was performed to analyze the grain gradation of different specimens, and a compression experiment was executed to compare and analyze the compression characteristics. The results show that the nonuniformity coefficient of mixed gangue is 55.2 and the curvature coefficient is 1.53, which significantly improve the grain gradation of washed gangue. The degree of relative compaction of mixed gangue is 1.226, which is significantly lower than that of washed gangue, which is 1.33. The deformation modulus of mixed gangue is 23–135 MPa, which is better than that of washed gangue (26–100 MPa), indicating that the compressive resistance of mixed gangue is significantly improved. The case study of the Tangkou mine suggests that mixed gangue greatly promotes the consumption of wasted gangue and can effectively control the surface deformation.
Highlights
Filling mining is a type of ecological protection mining technology that has been developed in recent years
The usage of this technology can process coal gangue and fly ash, two solid forms of waste from coal mines, and solid waste around cities while replacing coal resources under buildings such as villages, railways and overlying aquifers, and on floor pressurized water. This is a type of scientific coal mining technology that is in line with the ecological mine development model of “lucid waters and lush mountains are invaluable assets,” advocated by President Xi Jinping, with great promotion and application prospects (Hu and Guo, 2018; Qian et al, 2018; Wang et al, 2018; Dong et al, 2019; Ma et al, 2019; Wang et al, 2020a; Dong et al, 2020; Liu et al, 2020; Ju et al, 2021)
Through the screening experiment of gangue filling materials, the gradation characteristics of washed gangue are optimized to obtain gradation groups of gangue conforming to engineering applications
Summary
Filling mining is a type of ecological protection mining technology that has been developed in recent years. The particle size of washed gangue and crushed gangue in coal mines is similar to that of gravel soil, so the evaluation standard of gravel soil is adopted as that of a reasonable gradation of fully mechanized solid filling gangue in this study. The main mining area is the third upper coal seam, located in the middle of the Shanxi unit, with a full thickness of 2.63–5.11 m
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