Research On The Reasonable Offsets Value For The Close Distance Coal-seams With United Mine Way In Zhaojiazhai Coal Mine

Due to the different conditions in the formation of coal, coal seam occurrence conditions vary, and seam thickness from zero meters to hundreds of meters. Which can be taken from one layer to the layers of dozens of layers, the distance between the seams of varying sizes, each seam between the top floor lithology and angle differences are also very diverse. Close-seam mining methods commonly used "layered sub-mining" and "layered with mining." The upper of Zhaojiazhai mine close-seam is ?3 coal seam and lower seam is ?1, if using layered sub-mining, ?3 is a thin coal seam, and ?1 is a thick coal seam, if the ?3 coal seam is mined firstly, the replace of mining face is more difficult, which will affect mine production capacity. If the ?1 coal seam is mined firstly, the upper coal-seam is vulnerable to damage because the small distance between the coal-seam,, so that the recovery is not easy to face. Therefore, the same scene is used hierarchical manner mining exploitation. In order to ensure the safety of the stope face and the lower coal seam mining face when the upper and lower seams of two face, it need to maintain a reasonable level of offsets.In this paper, through the establishment of the conventional coal distance model in joint exploitation of close-seam distance, and reasonable distance of ?1 and ?3 coal-seam in mathematical solving was calculated, and a reasonable distance of 40 m was made. Using Numerical simulation FLAC3 D, along with the impact of the excavation face 31118 to 12210 cut open face, the mutual influence between two different face to keep away from different distance were analyzed, and the simulation results showed that reasonable distance of the two face is 30 m to 40 m, no longer interact with mining basicly. Meanwhile, in the site, a dynamic instrument roof of 12210 face roof to detect the subsidence monitoring, and multi-point displacement meter were used to monitor two face deformation of the roof and floor rock movement, as well as two mining hydraulic support set load boxes, monitoring of two different face in keeping offsets, the hydraulic support load changes, and two cycles to face pressure were analyzed. Through the above measured data, it can be found that after 31118 face exceeds 30 m than 12210 face, two face roof and floor rock movement deformation gradually stabilized, and the two face hydraulic support load relative to other offsets lower case, no longer have significant changes, 12210 work face pressure cycles at lower pressure still occurs regularly. Through a comprehensive analysis of the above methods, a reasonable distance of Zhaojiazhai two close-coal mined from the joint face should be maintained at about 40 m. Solving practical problems in Zhaojiazhai coal seam mining, provide a reference for reasonable distance of the joint exploitation in close-seam mining and roadway layout designed.