Analysis of the roof damage range in close-proximity gently inclined coal seams mining and the feasibility of upward mining

Abstract

Abstract In view of the feasibility of upward mining under the influence of repetitive mining for the close-proximity gently inclined coal seams, combined with the engineering geology of the coal seams in the south area of Xin’an Coal Mine, a formula for the depth of rock mass failure above the working face roof was proposed to investigate the continuity and integrity of coal seams 2−3 after the mining of the underlying coal seams. The characteristics of the overlying rock collapsed and the deformation law of the rock stratum sinking were analyzed through the similar experiments of physical simulation, to prove whether or not it is technically feasible to mine upward for the coal seams. Numerical simulation software is used to simulate the spatial distribution of mining stress field and stress transfer law of rock layer in the process of coal seams mining. The study shows that coal 2−3 is located within the lower coal seam fissure zone. The rock layer at the bottom of the working face has a certain bearing capacity, and can still maintain good continuity under the influence of repetitive mining. The stress concentration area of coal 3 up-slope mining develops continuously to the upper left rock body, and the peak of stress concentration is getting closer and closer to the coal wall, and the stress of coal 2−3 bottom plate and coal 2−3 top plate does not fall back significantly after the peak of stress occurs. The degree of rock fall and damage after mining is small, meeting the conditions required for upward mining. The results of the study provide a reference for the analysis of overburden structure and feasibility assessment under similar coal seams upward mining conditions.

Keywords

• Close-proximity gently inclined coal seams
• Upward mining
• Depth of rock mass failure
• Characteristics of the overlying rock collapsed
• Stress transfer law of rock layer