Investigation of longwall caving method efficiency in inclined thick coal seams by physical modelling

The longwall top coal caving production methods, which are widely used throughout the world in the production of thick coal seams, are applied in two different ways in the slope of the seam in inclined thick coal seams and by forming a face in the horizontal thickness of the seam, which is also called the horizontal section top coal caving production method in the literature. In the longwall top coal caving production method, which is applied by forming a face from the horizontal thickness of the seam, in addition to the top coal losses on the back of the face, which is the most widely researched subject in the caving methods, another top coal loss zone is formed above the tail part of the face. Although the top coal loss in this region significantly affects the efficiency of the method, no other study has been found in the literature, except for the study in which the effect of two different support unit drawing sequence on the top coal loss in this region was investigated using a 2D physical and numerical model. For this reason, within the scope of this thesis, the efficiency of the longwall top coal caving production method was investigated with a physical model developed within the scope of the study and which can be used in 2 and 3 dimensions. In order to test the suitability of the developed physical model for laboratory tests, firstly, field studies were carried out in Alpagut Dodurga Lignites underground enterprises, and then the physical model was run with the data obtained from the field. As a result of the studies, between the field data and the physical model data; 93.71% of the top coal loss, 93.4% of the rock mix ratio and 93.63% of the top coal flow angle were determined. Then, within the scope of the study, a total of 50 physical model tests were conducted, 7 of which were 2-dimensional and 43 of which were 3-dimensional. In the tests carried out, the effects of the top coal height, coal seam slope and face slope parameters and the change in the drawing sequence of the support unit, similar to the study in the literature, on the efficiency of longwall top coal caving production method were investigated. In the tests performed at 5 different top coal heights (4, 6, 8, 10 and 12m) and 6 different coal seam slopes (32, 38, 45, 52, 60 and 70°), it was determined that the top coal loss, which decreases with steepening of coal seam slope, increases with an increase in the top coal height. In horizontal and 10° face slope tests, it was found that the rock mixture ratio increased with an increase in the face slope, while there was no significant change in the top coal loss. The effect of the change in the drawing sequence of the support unit on the method efficiency was investigated in 2 and 3 dimensions in the physical model. In the 2-dimensional tests, 7 different support unit drawing sequences were used, and it was determined that the most ideal result, the number 5 support unit drawing sequence design (1-5-9-13-3-7-11-2-4-6-8-10-12-14) reduced the top coal loss by 7.89% (from 43,1% to 39,7%) and the rock mixture ratio by 44.8% (from 46,4% to 25,6%) compared to the drawing sequence of the support unit applied in the field. After the 2D physical model tests, the design number 5 was tested 3 times in 3D in the physical model and it was found that there was a 22.6% (from 12.4% to 9.6%) reduction in top coal loss and an 18.3% (from 65.4% to 53.4%) reduction in rock mixture ratio compared to the drawing sequence of the support unit applied on the field.