Quantitative criterion on coordinated ascending mining in close multiple “thin-medium-thick” coal seams

Kaiping coalfield consists of five “thin-medium-thick” recoverable coal seams in 80 m distance in Kailuan Coal Group, China.In order to achieve a safe and high-efficiency mining of this type coal seams, it is necessary to utilize the coordinated ascending mining and descending mining method.The key issue is how to measure the feasibility of ascending mining on coal seams with multi-level gobs.This paper takes many years’ ascending mining experience in Kailuan coal group as the research background.Methods such as theoretical analysis, statistics and field measurement are used to study the disturbance damage in ascending mining.Comprehensive damage discriminant index on ascending mining is proposed through the method of mining impact coefficient and ratio of interburden thickness and buried depth, and combined with other significant factors, such as multiple coal seams mining disturbance, distribution of overburden, physical and mechanical properties of rock strata, and fracture characteristics of overburden.The quantitative discriminant and evaluation system for coordinated ascending mining is established.A regional division method for the feasibility of ascending mining is proposed through the statistical analysis of 30 ascending mining cases.Drilling sight and Ground Penetrating Radar detection techniques are applied to measure the development and damage of overlying fractures.The range of caving zone is 15.4-21.2 m and the subsidence of overlying layer is 0.1-0.4 m in the observation section, which verifies the rationality of the ascending mining in 1692 panel of Qianjiaying Mine.The feasibility of ascending mining is analyzed by 66 drill hole observations in Fangezhuang Mine, which effectively predicts several dangerous areas and guides the project of ascending mining from No.12-1 coal seam to No.9 coal seam.Meanwhile, the definitions of “close coal seams”, “ultra-closed coal seams” and “multiple coal seams” are given by the research in the discriminant of ascending mining feasibility.In Kailuan Mining area, the method has achieved a remarkable effect in the engineering practice and provides a new theoretical basis for a safe and efficient recovery of the close multiple coal seam resources.