Numerical Analysis of Air Leakage Characteristics of Coal Seam Goaf Close to Thin Band

Abstract

This paper aims to research the air leakage of coal goaf near to thin band in Nantun Coal Mine. With using PFC3D numerical simulation software and establishing close distance coal seams mining numerical model, it analyzes roof migration characteristics of lower coal seam during mining and researches the law of development of roof air leakage passage in goaf; It also analyzes the changing situation of porosity of goaf in upper coal seam and researches the law of leaking oxygen expansion of goaf in upper coal seam. It is indicated from the research results that the curve and subsidence of main roof on working face forms fractures and cracks in its interior causing the air leakage passage between upper coal seam and lower coal seam. With the fracture of lower coal seam roof, the range of air leakage passage of goaf expands rapidly. And with the periodic fracture of roof, the air leakage passage moves forward continuously to prompt the leaking oxygen of lower coal seam to go into the upper coal seam goaf, and this is good for the spontaneous combustion of remaining coal body. Before the first weighting of main roof, the porosity of No. 3 upper coal seam goaf almost has no change; during the period of the first weighting of main roof, the porosity in No. 3 upper coal seam goaf close to palisades becomes big; with the periodic caving, the porosity of No. 3 upper coal seam goaf appears periodic enlargement and movement, and this is good for the diffusion of leaking oxygen in upper coal seam goaf and intensifies the spontaneous combustion of remaining coal in upper coal seam goaf.