Abstract:
The average distance between the Ⅲ-2 coal seam and the Ⅳ-2 coal seam in Dingjialiang coal mine is 35 m, in the early stage of construction, the lower IV-2 coal seam is mined in order to meet the economic benefits.As the mining of the Ⅳ-2 coal seam is nearing completion, the Ⅲ-2 coal seam above the goaf needs to be mined.This paper uses theory to analyze the feasibility of upward mining of the Ⅲ-2 coal seam and the law of underground pressure at the working face, numerical simulation analyzes the damage state of the surrounding rock during the mining of the Ⅳ-2 coal seam and the Ⅲ-2 coal seam, and observes the law of the appearance of underground pressure during the mining of the Ⅲ-2 coal seam.The results show that the height of the caving zone caused by coal mining of Ⅳ-2 coal seam is 7.20-11.60 m, and the height of the fracture zone is 31.05-42.05 m; after the Ⅲ-2 coal seam is mined, the coal pillars left in the lower goaf are slowly destroyed, and the fracture zone between the Ⅲ-2 coal seam and the Ⅳ-2 coal seam is connected, but the surrounding rock between the layers is generally stable, slowly lowering, and no large-scale collapse phenomenon.Verifying that the Ⅲ-2 coal seam is feasible for upward mining under certain safety measures; under measures such as closing the lower goaf, shortening the length of the working face to 100 m, and speeding up the mining speed during the actual mining process of the Ⅲ-2 coal seam, the initial pressure step is 49 m, the periodic pressure step is 19.9 m, and the dynamic load factor is about 1.3, and the rock pressure is obvious.