Numerical Simulation Study on Technology Optimization of Large Section High Fully Mechanized Caving Mining in Vertical Coal Seam

Wudong Coal Mine West Mining Area near vertical coal seam adopts horizontal section top−coal caving. In order to improve the production efficiency, the working face with short extension can be replaced by appropriately increasing the height of horizontal section. Therefore, it is necessary to study the top coal migration law of horizontal section top−coal caving in near vertical coal seam under the condition of large section height and optimize the coal caving technique to improve the top coal recovery rate. Combined with the field measured data, the model of coal drawing method under the condition of top coal size distribution of each layer is established. The top coal migration law in the process of initial coal drawing and periodic coal drawing under the condition of large section height are obtained by the Particle Flow Code numerical calculation. The top coal recovery and coal loss of each coal drawing parameter and order are analyzed, and the reasonable coal drawing technique suitable for B3−6 working face of Wudong Coal Mine is put forward. The results show that under the condition of large section height, the bottom of the coal−gangue boundary has a tendency to deflect to the right side during the periodic coal drawing process. The advance of the drawing opening position leads to a small amount of coal drawing in the subsequent multi−steps, and the coal−gangue boundary is seriously lagging behind the drawing opening position. The area of remnant coal is large. Therefore, excessive coal drawing can be appropriately used to alleviate the degree of demarcation of the boundary. When the mining height is 6 m, the development of coal drawing body and the fluidity of top coal are better in the early stage of periodic coal drawing, and the area of remnant coal is small. When the coal drawing interval is 2.4 m, the discharge amount of coal for each step is more and it is helpful to alleviate the problem of too fast seeing gangue. The coal drawing of “subsection drawing with large interval” can effectively reduce the influence of coal−gangue boundary line. The area of remnant coal is the smallest and the recovery of top coal reaches 93.23%.