Caving law of the coal and rock in the end zone of the fully mechanized caving face and its rational technological parameters

To maximize the recovery of the top-coal from the end zone, with the consideration of the position of hydraulic support of the end zone in the working face, support type, and the geographical conditions and technological conditions of working face, the three-dimensional model for carving coal in end zone was established, and the influence of different region of coal carving and parameters on the law of coal and rock flow down as well as the top-coal recovery rate was analyzed. Research has found that with the increase of the number of end zone hydraulic support carving coal, the displacement vector and migration scope of coal gangue increase obviously, the stress transfers to the forward of working face, roadway and coal pillar, the coal-gangue separatrix becomes unclear, the coal carving ratio decreases and the refuse rate increases; based on the top-coal recovery rate and the influence of coal carving on the stability of the roadway, the end zone is further divided into three zones: zone of easy coal carving, zone of less easy coal carving, and zone of least easy coal carving, with the first two as the main zones for coal carving in the end zone. Based on the research results, the principle of coal carving in end zone is put forward, the techniques and related parameters of coal carving in end zone are decided, and the field application has achieved good technical and economic effect. © 2017, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.