Study On The Optimum Position Of Roadway Of Middle Residual Coal Seam Between The Upper And Lower Longwall Goaf

With the continuous exploitation of coal resources,its reserves are also decreasing.In order to meet the long-term energy demand of sustainable and high-speed development in China,the remining of residual coal has gradually been put on the research agenda.There are many kinds of residual coal due to the condition of mining technology in the past.According to the related data,the reserve of middle residual coal in the compound residual mining area is higher,and it is widely distributed.Roadway is the premise and key to ensure the safe and efficient production of coal face.For the mining of middle residual coal in the compound residual mining area,the surrounding rock stress environment of the mining roadway is complex and deformation and destruction of the mining roadway are serious because of the influence of mining in the upper and lower coal seam..Therefore,the reasonable selection of the location of the mining roadway is an important factor to realize the safe remining and roadway control in the middle residual coal mining.In this paper,the No.10 middle residual coal in the compound residual mining area in Jinhuagong coal mine in Datong mining area is taken as the research object,and the laboratory test,theoretical analysis,similarity simulation and numerical simulation are adopted comprehensively to study the reasonable arrangement of the coal mining roadway in the middle residual coal.The main research contents and results as follows:(1)A method based on three factors— failure range,stress distribution and fracture distribution—is proposed to determine the reasonable position of the working face roadway of the residual coal in the composite caving area.First,judge the mining safety and recoverability of the middle residual coal by analyzing whether the failure extent of the interlayer rock caused by the upper and lower coal seams is spread to the middle residual coal.Then,through theoretical analysis and simulation experiment,the area of the fracture-concentration area,the stress superposition area and the high stress change rate area are obtained.Based on these,a reasonable roadway layout area is determined which avoid the above three areas.Finally,the failure characteristics and surrounding rock deformation of roadway at different horizontal positions are analyzed,the reasonable location of the middle residual coal roadway is got.(2)By similar simulation and numerical simulation,the failure extent of interlayer rock caused by mining of upper and lower coal seam has no effect on the residual coal of Jinhuagong.Taking the edge of the coal pillar as the center,horizontal distance in the range of 5~20 m is fracture-concentration area;horizontal distance in the range of-10~10 m is stress superposition area,horizontal distance in the range of 10~35 m is stress decreasing area,stress change rate is greater which have significant influence on the stability of roadway,its horizontal distance in the range of-15~20 m.Therefore,the reasonable roadway layout area is more than alternate exterior entry 15 m or alternate internal entry 20 m.(3)By analyzing the damage characteristics and the deformation of surrounding rock of roadway in different positions When the horizontal distance is 20 m,the deformation of surrounding rock of roadway is minimum and stable.The reasonable horizontal distance of the No.10 middle residual coal seam roadway in Jinhuagong coal mine is 20 m considering comprehensively.(4)The analysis of the influence of different upper and lower interlayer space on the deformation of surrounding rock of roadway can obtaine that.In the range of-15~0 m coal pillar,with the increase of the relative interlayer space,the influence of the middle residual coal with the stress caused by the pillar is decreasing,the deformation of surrounding rock of roadway is decreasing;In the range of 0~30 m goaf,with the increase of the relative interlayer space,the pressure relief grade of the middle residual coal in the range of goaf by the lower and upper coal mining is decreasing,the deformation of surrounding rock of roadway is increasing.