Analysis of coal drawing law and parameter research in shallow buried double hard and extra-thick coal seam

The coal resources in Xinjiang are shallowly buried, the coal seam is thick, resulting in poor top coal caving and drawing. And the roof is overhanging in a large area, which makes it impossible to achieve safe and efficient top coal mining. And at present, there are few related researches on efficient coal drawing in fully mechanized working face of shallow buried double hard and extra thick coal seam. In order to solve the above problems, taking 110501 fully mechanized working face of Yushuling Coal Mine as engineering background, the paper studies the coal drawing law of shallow buried double hard and extra thick coal seam, so as to determine reasonable mining-drawing rate and coal drawing technology, and improve the recovery rate. FLAC3D software is used to analyze the coal and rock failure law in the mining process of fully mechanized working face, so as to design reasonable mining-drawing ratio. The results are listed as follows. ① With the increase of the mining height of the working face, the yield failure coefficient of the top coal and the coal wall continues to increase, and the maximum value of the advance support stress and the affected area of the coal wall on the working face gradually increase. ② Considering the stability and caving and drawing of top coal and coal wall, the designed mining height is 4.0 m, the top coal drawing height is 4.6 m, and the mining-drawing ratio is 1∶1.15. The top coal drawing law of fully mechanized working face is analyzed by using PFC2D software, so as to design reasonable coal drawing technology (including the design of coal drawing step distance and coal drawing mode). The results are listed as follows. ① The gangue content of ‘one coal mining and one top coal drawing’ is higher than that of ‘two coal mining and one top coal drawing’ and ‘three coal mining and one top coal drawing’, but the overall drawing rate is higher than that of ‘two coal mining and one top coal drawing’ and ‘three coal mining and one top coal drawing’ due to the small coal drawing step distance. Therefore, the coal drawing step distance of ‘one coal mining and one top drawing’ is selected. ② Compared with two rounds coal drawing, single round coal drawing has higher coal drawing speed, but gangue content is higher and coal drawing rate is lower. Compared with two rounds sequential coal drawing, the two rounds interval coal drawing has a higher drawing rate. Therefore, the tow rounds interval coal drawing method is selected. The designed mining drawing rate and coal drawing process are applied to the engineering practice of 110501 fully mechanized working face, the results show that the top coal drawing rate of this working face is 82%-87%, the average drawing rate is higher than 82%, and the coal drawing effect is good.