Ecological-economic aspects of mining thin coal seams in the Western Donbas

The paper draws attention to the ecological-economic aspects of mining thin coal seams in the strategic coal-mining region of the Western Donbas and studies their causes and consequences in detail. It has been analyzed and determined that as a result of coal mining with complete caving of rocks, the processes of the earth’s surface subsidence above the mine fields occur. Due to the proximity of groundwater to the surface, waterlogging of territories and a change in the landscape occur. Using analytical calculations, it has been determined that the total surface subsidence value above the mine field of one of the Western Donbas mines is 1.2 m, which, according to the monitoring of environmental authorities, correlates well with the range of subsidence values in the region of 0.7-1.4 m. The places and parameters of rock dumps accumulating on the earth’s surface in coal mines are identified and analyzed, and the sources of waste rock formations in the technological system of coal mines are also studied. It has been revealed that the largest ingress of all waste rocks to the surface is caused by the stope operations conducted with undercutting of bottom rocks – 39% and underground mining operations to prepare new coal reserves for extraction – 33%. To date, it has been found that the volumes of waste rocks generated in mines are 1.5 times higher than the volumes of their utilization, and the prospect of disturbed land reclamation is limited in time, which, with today’s mining technology, will lead to an increase in their accumulation again. Based on a comprehen- sive study of the mined coal seam structure with a complex texture, using the example of one of the mines, it has been revealed that in the formation of operational ash content, the friable roof caving amounts to 13.0%, the seam rock interlayers – 19.2%, the coal seam natural ash content – 12.8%, and the seam bottom rock undercutting – 55.0%. A close linear relationship has been determined between the value of bottom rock undercutting with a shearer based on collected mine data and the indicator of mined coal operational ash content, which confirms the greatest importance of this factor. It has been proved that the most important factor influencing the formation of the mined coal operational ash content is the undercutting of the seam bottom rocks by a shearer, and with a 2-fold decrease in the ash content of coal, its energy potential increases by 1.25 times. Possible scenarios for the coal mining development in the Western Donbas are considered and a rational direction for solving the leading ecological-economic problems of underground mining of thin coal seams is proposed.