Development and prospect of mining methods and equipment in underground coal mines in Yulin area

Yulin, Shaanxi Province is an important coal production base in China and plays an important role in national energy security and ensuring coal supply. Based on the current mining situation of underground coal mines in Yulin area, this paper systematically analyzes the innovative practices and development trends in coal mining methods and mining equipment in this area. In terms of coal seam occurrence, the coal seam dip angle of Yan’an Formation is nearly horizontal and its structure is simple, and the thickness of coal seam ranges from 0.80 m to 13.06 m, thus forming diversified mining conditions for medium-thick, thick and extra-thick coal seams. The coal seam roof is characterized by “stable direct roof and hard basic roof”. In terms of output, raw coal output has increased from 1 million tons in 1978 to 637 million tons in 2025, the national proportion has increased from 0.17% to 13.1%, and there are 17 ten-million-ton mines. Coal output has maintained a high growth trend for a long time and has become an important supporting area in the national coal supply pattern. In terms of coal mining methods, it has gone through five stages: short-wall mining, early stage of long-wall mining, popularization of long-wall mining, intelligent exploration and green mining. The overall situation shows that the working face has changed from short to long, the mining height has changed from small to large, and the equipment has evolved from import to domestic production and control from manual to automatic. Four core technical systems have been built for fully mechanized mining at ultra-long working face in medium-thick coal seam, fully mechanized mining in thick coal seam with large mining height, fully mechanized mining and fully mechanized top-coal mining with ultra-large mining height in extra thick seam and filling mining. In terms of equipment development, the working resistance of hydraulic support is increased from 6 000 kN to 29 000 kN, the support height is increased from 3.5 m to 10.0 m, the total power of shearer is increased from 850 kW to 3 350 kW, and the transportation capacity of scraper conveyor is increased from 1 500 t/h to 8 000 t/h. Key equipment has realized the leap from introduction and digestion to domestic dominance, supporting the continuous breakthrough of mining parameters. Taking 450 m ultra-long working face in Xiaobaodang No.2 Coal Mine, 10 m extra-high mining height fully mechanized mining in Caojiatan Coal Mine, 7 m extra-high mining height fully mechanized caving in Jinjitan Coal Mine and filling mining in Mahuangliang Coal Mine as typical cases, corresponding to three different conditions of medium-thick coal seam, extra-thick coal seam and coal trapped under buildings (structures), demonstrating the coal mining technology and equipment level of Yulin area under different coal seam conditions. At the same time, the main technical challenges are deeply analyzed: the disasters of strong ground pressure and rock burst caused by deep mining are increasingly prominent; the problems of interlayer disturbance and support under goaf in the mining of close-distance coal seams have not been fundamentally solved; the re-mining of residual coal in early room-column goaf faces the risk of coupling roof instability and multiple disasters; and water-retaining mining and filling mining in ecologically fragile areas are still subject to technical and economic bottlenecks such as high cost and lack of materials. Looking forward to the future, the coal mining technology in Yulin area will develop in depth in five directions: efficiency, intelligence, precision, green and low-carbon, providing a demonstration for the intelligent and efficient development and green and low-carbon transformation of coal mines in the western region.