Study On Reasonable Mining Method Of 11# Ultra-close Coal Seams In Taishanlongan Coal Mine

Close distance coal seams are widely distributed in China,and how tochoose the reasonable mining method of close distance coal seams is a problem that many mining areas are faced.As the coal resources has been largely mined for years,the occurrence of relatively good conditions of coal resources are nearing completion.In order to improve the coal production and increase the service life of the mines,for the mining of close distance coal seams is receiving more and more attention from the mining industry.The distance of the 11~#ultra-close coal seams is only 2.41m inTaishanlongan Coal Mine,how to choose the reasonable mining method is very important.Reasonable mining method can not only ensure the safe and efficient production of the working face,but also can effectively reduce the production cost and improve economic efficiency.In this paper,according to the actual conditions of 11~#coal seams in Taishanlongan Coal Mine,two mining methods are proposed:the downward mining and the full-mechanized caving mining.Through theoretical analysis and numerical simulation,the feasibility of the two methods is demonstrated,and the most reasonable method is chosen.The main conclusions are:(1)If the downward mining method is selected,the roof the lower coalseam is damaged before mining.According to the theory of slip line field theory,the maximum damage depth of upper seam floor is 0.979m,which is less than the average thickness of the interlayer rock,and the lower seam still has a complete roof of 1.431m thick,based on past experience,the safe mining of lower coal seam can be guaranteed;According to the mechanical model of interlayer roof,determines the stability of interlayer roof thickness for loser distance coal seams,the results show that without considering the premise of hydraulic support,the safety thickness is not less than 2.32m,on the opposite,it can decrease to 1.52m,Thus,it can guarantee the safety mining of the lower coal seam with taking special measures;Using UDEC numerical simulation software,the stability of the roof,the motion characteristics of the overburden and the applicability of the stents are simulated and analyzed under the conditions of the support,the above results are further verified.When all of these problems are considered together,after the appropriate measures are taken,the downward mining method can be adopted in11~#ultra-close coal seams in Taishanlongan Coal Mine.(2)To determine whether the fully mechanized mining method can beused,it is necessary to make a reasonable prediction of caving characteristic.Generally speaking,the main factors influencing the caving characteristic are included mining depth,seam thickness and strength,dirt band,coal fracture development degree,roof conditions and so on.In this paper,by using fuzzy mathematics classification and failure coefficient method,reasonable projections of caving characteristic,and integrated the actual situation,think the 11~#coal seam belongs to?class,it can use the fully mechanized mining method after taking some appropriate measures to the dirt band.Using FLAC3D numerical simulation software,the influence of the thickness of the dirt band on the caving characteristic was analyzed and studied.Taking into consideration,it is considered that the 11~#coal seam of Taishanlongan Coal Mine can use fully mechanized mining method when the interlayer roof thickness is less than 2.4m.(3)According to the actual conditions,reasonable selection of miningequipment of two mining method,and compare the economic benefits of the two methods,the results show that although the initial stage of the downward mining is larger,the economic profit is higher.Compared with the technical and economic aspects,it is considered that the downward mining is more suitable for the actual conditions of the mine.