| The paper aiming at the specific conditions of hard roof and hard coal seam in Datong mining area Yungang mine adopts composite measures of "water injection—blasting" joint weakening to top coal and pre-splitting blasting to the roof and overcomes the insufficiency of the single weakening measures and plays advantage of the various weakening measures then forms a set of effective top-coal weakening technology and the caving process to improve the putting ability of two hard thick coal seam fully-mechanized caving top-coal.The top-coal weakening effect at working face 8818 has been forecasted and analysised using RFPA software. Under the dual role of water pressure and blasting pressure, horizontal effective impact range is around 6.0 m and the coal loose effect is significantly better than the single top-coal weakening of pre-injection and blasting weakening. According to the theory and numerical simulation calculation to the stope overburden rock movement parameters, upper roof first weighting step reduces to 30 m from 55 m after weakening the working face and cycle breaking step reduces to 10 m from 20 m. At the same time, joint weakening the fully mechanized top-coal migration and stress distribution rules are in studying basing on the theoretical analysis and numerical simulation method and the stope stress concentration factor is decreased obviously after the top-coal weakening. Through working face mining engineering practice, "water injection—blasting" joint weakening parameters and process are optimized constantly, At last the joint weakening parameters that adapt to the Datong two hard thick coal seam mining area special conditions is getted.The studies show that the top-coal putting ability increased from 0.603 to 0.812 after adopting joint weakening measures. It is of great significance to increase fully-mechanized top-coal release rate in Datong mining area, increase the recovery rate of coal resources and realize high production and efficiency. |
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