Study Of The Strata Pressure Behavior Law And Face Length Optimization In Initial Miniing Stage Of Fully Mechanized Top-coal Caving Face With Large Mining Height In Changchunxing Coal Mine

The inclined length of working face is an important factor to restrict the high yield and high efficiency production of fully mechanized top coal caving mining. At present, the study which research the regularity of strata pressure during the initial mining period on the working face length of fully mechanized top-coal caving mining with large mining height is less. According to the geological data and the measured value of roof pressure in 4 different faces of Changchun Xing coal mine, this paper analyzes the end resistance of bracket, dynamic load factor, and the degree of macroscopic strata behavior in the initial-pressure period of the main roof. It is found that there are some problems in the strata pressure under different surface length, and analysis the reasonable range of face length that based on measured data is 140-230m.Based on the basic geological conditions and mine pressure monitoring data of the 301 working face, the roof structure model is established, and the roof movement pattern is analyzed, which provides the theoretical basis for the study of the strata pressure law and numerical simulation.The numerical simulation software FLAC3D is used to simulate the roof subsidence value and the advanced abutment pressure of the working face with different length and different working conditions.Under the given support pressure, the roof subsidence value is used as an important index to judge the effect of the roof support in the working face, and the reasonable range of the working face under the specific load of the roof is 140-200m.Based on the influence of the advanced abutment pressure on the crushing degree of the top coal, the variation of the advanced abutment pressure in the face with different length is analyzed, and the optimal range of the working face length is more than 200m.According to the plate fracture theory and the voussoir beam theory,using the length-coefficient method and combined with the support strength of the working face support, it is concluded that the range of working face length is less than 198.5m.It combines the strata pressure behavior, numerical simulation and theoretical research in initial mining period. according to the bearing capacity of support in Changchun Xing coal mine, the optimal length of the working face with high yield and high efficiency is identified. It is 200m, which is determined by the specific load conditions.