Study on mechanism and improvement technology of Top coal loss in horizontal sublevel fully mechanized caving mining

Abstract

In view of solving the problems of large top coal loss and low recovery rate in the traditional caving process of horizontal section fully mechanized caving mining, taking the fully mechanized caving face of steeply inclined and extra-thick coal seam in Yimen Coal Mine as the engineering background and the research method of numerical simulation and field measurement was used to study the coal gangue flow characteristics under different coal caving directions and different number of coal caving ports at the bottom plate side, revealing the mechanism of top coal loss and proposing the technology to improve the recovery rate. The results show that the action time of top gangue and the ‘ rotation ‘ of coal gangue flow in the triangle coal area jointly promote the release of triangle coal in the bottom plate, which makes the coal gangue interface steeper and the release rate higher when the coal is released in the lateral direction of the bottom plate; adjusting the number of opening coal mouths when the initial coal caving at the floor side can coordinate the top coal caving speed, gangue down-channeling speed and the closing time of the coal caving mouth. When the first coal caving opens two coal caving mouths, the recovery rate of bottom triangular coal is the highest. Yimen Coal Mine adopted the floor lateral roof side caving and double-mouth caving technology. Compared with the original scheme, the top coal recovery rate of the working face increased by 3%, and the top coal recovery rate of the floor triangle area increased by 7%.