Research On Mining-entries Supporting Technology In Steeper Thick Coal Seam Of The Qaidar Coal Mine

Compared with the horizontal and gently inclined coal seam, the occurrence and mining conditions of steeply inclined thick coal seam more complicated. And the roadway supporting technology is one of the most important research topics for safe and efficient mining of the steeply inclined thick coal seam. According to the special geological condition and the deformation characteristics of mining roadway in the Qaidar coal mine, the methods of combining geological exploration,theoretical analysis, mechanical analysis, similar material simulation test,numerical simulation and field monitoring are adopted to study the deformation law and support technology of mining roadway in the sublevel working face of 204 mining area of Qaidar coal mine. The following conclusions and understanding are obtained:(1) According to the research status of steep inclined thick seam mining and combined with the characteristics of the steeply inclined thick seam in Qaidar coal mine, the influencing factors of surrounding rock stability in sublevel mining face of steep inclined thick coal seam were summarized. Also, the instability process of surrounding rock of roadway in steeply inclined thick seam was analyzed. Using the "cross arch" mechanical model, the relationship between the superimposed stresses of the mining roadway and the mining depth and the arch span was calculated under the condition of a certain inclination of the coal seam. It is found that the greater the superimposed length of the cross arch arch and the larger the mining depth are, the greater the superimposed stress is.(2) The method of similar material simulation test was used to study the stress evolution law of the roadway in the first and fifth sublevel working face. The stress of surrounding rock of mining roadway increases firstly and then decreases with the first sublevel working face advanced. The stress on the top of the roadway is larger,and the stress at the left side of the return air tunnel is greater. The caving characteristics of top and bottom of sublevel steep seam and the migration law of top coal were studied. The results show that the roof cavinghas certain periodicity and hysteresis, the mining of the lower section will cause the collapse of the uper sublevel coal rock mass, the range of damage extends upward to the top of the coal face roof, forming a sunken funnel". Finally, the stress characteristics of fifth section roadway surrounding rock mining with working face are studied. It is found that the stress is higher than the surrounding rock mass of the first section.(3) The numerical simulation method is used to analyze the change characteristics of the surrounding rock stress with the increase of mining depth of sublevel working face. The dynamic change laws of the stress and displacement of surrounding rock of roadway in five sublevel working face under different schemes were studied. The results show that the stress of the surrounding rock in the lower section of the roadway is superimposed by itself and the sublevel mining, and the stress of the surrounding rock of the roadway increases firstly and then decreases with the advancing of the working face. The horizontal and vertical stresses of the gateway were prominent, and the top, the inner side, the side and the corner of the roadway are the key areas of the stress concentration. Also, the deformation of roadway surrounding rock of roadway in roadway is larger than that of bottom return air lane.(4) By using the method of engineering practice, the optimized scheme obtained by numerical simulation was verified, and the relevant supporting parameters were determined. The deformation of surrounding rock is effectively controlled, and good results are achieved. The research results have certain significance for the study of the support technology of the roadway in sublevel working face of the steep inclined thick coal seam.