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Abstract
Based on the background of close coal seam mining in the Qianjiaying coal mine, Tangshan, China, the feasibility of the upper seam mining in complex underlaying goaf is analysed using the roof caving analysis and numerical method. The deformation of the mining seam and roadways is monitored and analysed by field measurement and 3D laser scanning. The deformation characteristics of #5 seam after mining 1378P, 2071P, 2072P, and 2091P working panels with a depth of 39–54 m below the #5 seam are analysed using roof caving analysis and numerical method. Results show that the maximum deformation of #5 seam in the superimposed area of the lower goafs reaches 2.5 m and the maximum deformation in the single coal goaf is 1.5 m. The maximum seam inclination is 1.9°. The subsidence of the floor of 1359P roadways is obtained by field measurement, and the result is consistent with numerical calculation. ZEB-HORIZON 3D laser scanner was used to measure and model the roadway deformation. Based on the analysis of multiple scanning data, the deformation of the 1359P roadways was obtained. Results show that the deformation of the surrounding rock of the roadway is not great, the maximum displacement of the roof fall is 30 mm, and the maximum rib convergence is 25 mm. It can be concluded that the #5 seam can be recovered in this complex underlying lower seams’ mining condition.
Highlights
Close multiseams mining refers to the coal seams with mutual influence
E lower seams’ mining causes upper seam movements and ground stress unloading, which introduce fractures influencing the stability of surrounding rock of upper seam [8,9,10,11,12,13,14,15]. e research of the upward mining method mainly focuses on the overburden damage analysis caused by lower seam mining and the deformation monitoring and strata control technology while upper seam mining. e former addresses the feasibility of upper seam mining
Multiple 3D laser scanning was carried out in the roadways using the ZEB-HORIZON 3D laser scanner, and the deformation of the upper roadways beyond lower seam coal mass, goaf, roadway, and coal pillars was evaluated to provide a basis for monitoring and strata control in the excavation. is paper conducts a case study of upper seam mining over complex lower seam conditions using theoretical, numerical, and field monitoring methods, which provide a reference for feasibility judgement and premining confirmation of upward mining under similar geocondition
Summary
Close multiseams mining refers to the coal seams with mutual influence. As excavation has greater impact on the roof than the floor, the downward mining method is often used to reduce the influence on adjacent seams [1]. Upward mining faces the challenges of upper seam and surrounding rock subsidence, fracturing and bending, gas imitation, and stress concentration directly above lower seam pillar [2,3,4,5,6,7]. E lower seams’ mining causes upper seam movements and ground stress unloading, which introduce fractures influencing the stability of surrounding rock of upper seam [8,9,10,11,12,13,14,15]. Jiang et al [18] obtained roof stress distribution using the continuous beam model under uniformly distributed load, which can be used to study the feasibility of upper seam mining above large goaf area
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