Abstract
To design underside protective seam strip layout. Similarity model experiments, numerical simulations and theoretical calculations are used to quantitatively study the pressure relief protection effect of different strip widths, dip angles and coal pillar widths of a thin underside protective seam under deeply buried conditions. The optimal strip width range is obtained according to the change law of strain during the mining process of the underside protective seam in a similar model experiment. The change law of the expansion of the protected coal seam is obtained and the fitting surfaces among the dip angle and strip width of the coal seam with the protection distance and pressure relief angle along the strike and dip of the protected coal seam are established according to the numerical simulation results of underside protective seam mining. It is concluded that the best pressure relief effect can be achieved when the dip angle is 16.7° and the strip width is 70 m. According to the stability threshold of coal pillars considered in strip mining theory, the coal pillar width is calculated to be 50 m. Similarity model experiments and numerical simulations of protected coal seam mining verify the pressure relief effect of the designed protective seam strip width and pillar width. A calculation method of the protective seam strip width, position and pillar width required by the specific width of the protected seam is proposed.
Highlights
The mine studied here is a coal and gas outburst mine, with a thin, deeply buried #4 coal seam, a complex geological structure including many faults, and poor economic benefits
The optimal strip width obtained by the numerical simulations is within the range of similarity model experiment results
The law that the pressure relief angle at the open-off cut side is greater than the pressure relief angle at the mining side obtained by the numerical simulations is consistent with the law of the breaking angle at both sides obtained by the similarity model experiment
Summary
The mine studied here is a coal and gas outburst mine, with a thin, deeply buried #4 coal seam, a complex geological structure including many faults, and poor economic benefits. Fang et al [51] studied the pressure relief protection effect of upper protective seam mining with different coal seam dips through similarity model experiments.
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