Research on mining plan of non-working high-level coal seam in open-pit mine with near-horizontal composite coal seam

Abstract

In the extraction of subhorizontal multiple coal seams using open-pit mining in China, the problem of coal seam in the high wall is commonly existed, but studies usually focus on the lower coal seam mining problem only. Based on the problem of implementing the mining of upper coal seams in non-working step, the initially formed inner refuse dump is used as the working platform, and the influence of the stability of the slope stability on the mining mode is also considered. It is proposed, in the premise of stable slope to form a pattern of “openings” and “ramps” stage by stage. In the actual production of open pit mines, combined with the requirement to meet the specific slope angle to ensure the overall stability of the highwall, making the maximum of economic benefit as the judgment criterion, the staged mining mode is divided into two types: recover coal pillars between the stages and retain coal pillars between the stages. By means of quantitative analysis, the theoretical criteria for the economic feasibility of the two are given, respectively, and the relationship between the net income obtained by the two mining methods and the thickness of the coal seam is discussed. The results shows that the net profit value (NPV) of different mining methods is positively correlated with the thickness of the coal seam, so the optimal mining method can be selected by analyzing the relationship between the thickness of the coal seam and the NPVs. The economic rationality of the mining method in the specific application should be checked according to the actual situation on site. Taking an open-pit mine as the engineering example: ① It is determined that the recovering coal pillar between stages is more economical, the net income is 63.853 million yuan, and extraction and stripping ratio of remnant coal in the non-working side is 0.758; ② By reducing the height of the coal pillar and increasing the corresponding slope angle of the stope and dump, economic benefit can be increased using the retaining coal pillar between stages. The results can be applied to similar open-pit mines. By reducing the waste of coal resources, the overall economic benefits of mining enterprises are improved while ensuring safe, green and efficient mining.

Keywords

• subhorizontal multiple coal seams
• open-pit mine
• upper coal seam mining
• recovery of coal pillar between stages
• retain coal pillar between stages