| China is rich in coal resources and the occurrence conditions of coal seams are complicated.With the development of science and technology,most coal seams with simple mining conditions are greatly reduced.At present,the mining is mainly aimed at coal seams with complicated mining conditions,of which the mining of close-range coal seams accounts for a large proportion.Downward mining is usually used for close-range coal seams,and the bottom plate of the upper coal seam is generally taken as the top plate when the lower coal seam is mined,so that the surrounding rock state of the lower coal seam will be greatly affected after the upper coal seam is mined.Influenced by the interlayer rock layer distance of the two layers of coal and the dip angle of coal seam,the floor strength of the upper coal seam is damaged to a certain extent after mining,and the coal pillar left over from the upper work flour will produce a local stress concentration area in the lower coal seam,which brings difficulties to the location selection of roadway and surrounding rock control during mining of the lower coal seam.This dissertation takes the occurrence conditions of the 3 upper and 3 lower extremely close inclined coal seams in Fucheng Coal Mine of Inner Mongolia as the research background.In order to ensure the stability of the 3 lower coal seam mining roadway,the roadway layout and surrounding rock control of the mining roadway under the goaf of the 25 extremely close inclined coal seam in dip angle of coal seam are studied by comprehensively using the research methods of theoretical analysis,numerical simulation,laboratory test and field observation.The main results of the study are as follows:(1)The natural equilibrium arch theory and 3DEC software are adopted to construct a three-dimensional structural mechanical model of the inclined stope,and the movement law of overlying strata on the inclined stope is analyzed.The protolith stress field distribution of the inclined stope is obviously complicated due to the influence of the inclination angle of the overlying cliff,and the dynamic distribution and evolution law of the mining induced stress field are obviously asymmetric along the working flour tendency.(2)By analyzing the stability of coal pillar,the calculation model of plastic zone of coal pillar left over from flour in the upper part of inclined coal seam is established,and the calculation formula of plastic zone width of coal pillar is obtained.Based on the actual geological conditions of Fucheng Coal Mine,the section pillar between 1301N and 1302N working flour on the 3rd is determined as a stable pillar.(3)Through theoretical calculation and numerical simulation,the distribution law of vertical stress and principal stress difference of bottom wall rock of residual coal pillar under different dip angles after upper coal mining is analyzed,which provides theoretical guidance for the selection of mining roadway location in lower coal seam.It is determined that under 25 dip angle of coal seam,the mining gateway in the lower coal seam is internally staggered,and the reasonable staggered distance between the two gateway of 1301N working flour under 3 is determined to be 9m based on the results of stress change equilibrium degree of numerical simulation.(4)According to the roof failure characteristics of 1301N working roadway in the 3rd lower part of Fucheng Coal Mine,the control principle of roof in the lower coal seam roadway is determined:(1)rapid load bearing,(2)lateral reinforcement;It is proposed to adopt "bolt+I-steel+single hydraulic prop" combined support technology to control the surrounding rock of roadway.Through numerical simulation and on-site mine pressure monitoring of the support technology,the feasibility of the support technology is determined. |
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