Study On The Mining Roadway Arrangement And Surrounding Rock Control Technology Of Ultra-close Multiple-seams Mining

With the rapid development of China’s coal industry, the degree of mechanization around the coal enterprises is promoting day by day, and mining intensity increases gradually. As a result, the coal seams with better burial condition have been dried up. As one of the main sources of China’s economic and social development, coal will still be greatly mining in a considerable period of time. At the same time, coal seams with worse burial condition, such as the combined mining coal seam group in very short distance, gradually come into people’s vision, and they have become a subject of coal mining.Due to the different coal-forming conditions, occurrence of very short distance coal seams is not same as well. The differences mainly contain the interlayer spaces, coal mediums, recoverable thickness and rock in the roofs and floors in different seams, etc. In the condition of combined coal seams mining, because of the short distance of the coal seams, upper coal mining will destroy continuity of the coal and integrality of the floor, which also means the roof of the lower coal seam, leading to inability of normal lower coal mining and a waste of resources. Therefore, to ensure the output of coal enterprises and safety of the coal mining in different seams, at the same time to reduce the coal loss rate, short distance seam roadway layout and surrounding rock control technology have become important factors affecting the safety and efficiency mining of coal resources during coal enterprises.Taking Lu Zi Gou coal mine of Shanxi Coal Transportation and Marketing Group as the research background, the paper made a combination of theoretical calculation, numerical simulation and mechanical model, to research and analyze the roadway arrangement and surrounding rock control technology of the3.1m distance coal seams. Conclusions through research the are as bellow:(1) Using ratio method and the "three zone" distinguish method to calculate surrounding rock failure depth of3.1m distance coal seams, ultimately the paper confirmed to use mining sequence downstream during coal seams groups in this geological condition.(2) Through theoretical analysis and establishment of mechanics model of residual coal pillar stability in very short distance coal seams, the analysis results showed that the residual coal pillar was the stable when the residual coal pillar width was2times longer than the length of limit equilibrium zone, which meant that a certain width of elastic core pillar was in the centre of the coal pillar.(3) Through the theoretical calculation and analysis of the length of limit equilibrium zone and elastic zone in the upper coal seam mining, it obtained the external offset formula of external offset roadway layout type. And through calculation and analysis of damage range of the floor, it obtained the inner offset formula of inner offset roadway layout type layout. Ultimately combining the geological condition of Lu Zi Gou coal mine, the paper determined that this coal mine was supposed to use external offset roadway layout type.(4) Through FLAC3D numerical simulation of external offset roadway layout type arrangement in upper and lower coal seam roadways of Lu Zi Gou coal mine, the paper analyzed the law of mining pressure and the stability of roadway surrounding rock with different staggers of3m,5m,7m,9m and12m,and eventually it determined that the safe and reasonable stagger for3.1m distance coal seam mining was9m.(5) Through the method analysis and establishment of mechanics model, the paper analyzed the roof stress situation in short distance coal seam mining to adopt bolt-mesh-cable combined supporting for roadway support with corresponding supporting parameters.