Investigation of the effect of caving height on the efficiency of the longwall top coal caving production method applied in inclined and thick coal seams by physical modeling

The longwall top coal caving (LTCC) production method, applied by forming a face in the horizontal thickness of the seam and also called horizontal section top coal caving, especially in studies originating from China, is widely used in the production of inclined and thick coal seams. In this production method, in addition to the top coal losses that occur behind the face in the traditional LTCC production method, and top coal loss zone occurs above the tail part of the face. Here, the caving height is an effective parameter in the top coal losses occurring behind the face and on the tail part of the face, and in this study, the effect of caving height on the efficiency of the LTCC method applied in inclined and thick coal seams was investigated. In the study, a physical model was used, which was tested with field data and achieved a minimum success rate of 93.4% in the test parameters. In order to determine the effect of the caving height on the efficiency of the LTCC method, a total of 15 tests were performed with the physical model in 3 different seam slopes. As a result of the tests, it was determined that the amount of top coal and waste rock drawn and top coal loss increased with the increase in the caving height value. On the other hand, it was determined that the rock mixture ratio first decreased and then increased with the increase in the caving height value. In addition, the flow angle of the top coal was determined as an average of 74.9° in the coal loss zone between the top coal and the floor and 73.4° on the gob. •Importance of caving height in LTCC applied in steeply inclined thick coal seams.•Applicability of physical modeling as research method.•Compatibility of the physical model with the field data.•Importance of coal seam slope and thickness in LTCC applications.•Effects of caving height on top coal loss and rock mixture ratio.