Investigation of the efficiency of longwall top coal caving method applied by forming a face in horizontal thickness of the seam in steeply inclined thick coal seams by using a physical model

Abstract

The longwall top coal caving (LTCC) is a widely used method for producing thick coal seams. This method is applied in two different ways in steeply inclined thick coal seams by forming a longwall at the horizontal thickness of the seam and the slope of the seam. In the LTCC method, the top coal loss is generally expressed as the coals remaining behind the support units after the face advance. However, in addition to this coal loss in steeply inclined coal seams, a coal loss zone is formed in the upper part of the tail of the face that is not affected by the top coal drawing process. In this study, top coal loss and rock mixture ratio in this region were investigated with a physical model developed. Field studies were carried out at Alpagut Dodurga Lignite Enterprises and the data obtained were tested in the physical model. Between the physical model data and the field data, 93.71% similarity in top coal loss and 99.8% similarity in rock mixture ratio were determined. In order to investigate the efficiency of the LTCC method, the effects of top coal drawn height, seam slope, face slope, support unit drawing sequence change parameters on top coal loss and rock mixture ratio were investigated. As a result, it was determined that the top coal loss increased linearly with the increase in the upper coal withdrawal height, the top coal loss decreased with the increase of seam slope, the face slope did not significantly affect the top coal loss and the rock mixture ratio decreased by 18.3% with the change in the drawing order of the support units. In addition, a new longwall design has been proposed in the study, and with this design, the top coal loss has decreased from 17.3% to 2% geometrically.