Rock Pressure Distribution And Roadway Stability Controlstudy Under Coal Wall Of Goaf

During the mining process of close distance coal seam mining， stressdistribution in the lower coal was affected by the upper coal excavation,among which the layout and stability control of roadway was the difficultproblems. So studying the reasonable layout and support of roadway, inaccordance with stress distribution in the lower coal, is of great importance forhigh production and high efficient mine. Taking the close distance coal seam inLuyukou mine as the research object, using theoretic analyses, numericalsimulation, engineering monitoring, and other research methods, layout andstability control of roadway in the lower coal was been systematicallyresearched based on the analysis of stress distribution in the lower coalaffected by the goaf. The results showed that:(1) Stress field in the lower coal was mainly the variation of verticalstress affected by stress in goaf of the upper coal. The theoretic analysesshowed the areas under goaf in the lower coal was the vertical stress relaxedareas, the areas4~25m under pillar was the high vertical stress areas and thevertical stress in high areas was about double that of protolith.(2) Stress distribution of the lower seam was less affected by uppermining height and the depth of coal seams group, while greatly affected by the Protogyakonov’s coefficient of the roof in the upper seam and the distancebetween the two coal seams. When the Protogyakonov’s coefficient of the roofwas high, vertical stress under pillar concentrated strongly, meanwhile verticalstress under goaf decreased obviously. Stress peak in the lower coal had asharp non-linear increase with the decrease of the distance between coalseams.(3) Due to the stress of goaf decreasing, vertical stress of roadwaysurrounding rock under goaf was low. Plastic areas distribution mainlyconcentrated in the roof but small and the deformation of roadway is alsolesser; the vertical stress in the two sides and shoulders of roadway under coalpilar influenced by transfered coal pilar’s bearing pressure increased sharplyand the roadway surrounding rock had a large shear failure area, deformationis huge.(4) Surrounding rock stability was good when the roadway in the lowercoal was located under goaf, while it was poor when the roadway in the lowercoal was located under pillar. In real project, it is better to make the roadwayin the lower coal located under goaf not pillar, and this can reduce the roadwaysupport work.(5)The two sides and shoulders of the roadway surrounding rock wereimportant support areas. While conventional support can’t meet therequirement of the roadway stability, changing roadway cross-section tovertical wall semicircular arch roadway, increasing diameter of bolt and cable,improving the pre-tightening force, making anchor located incline to theplastic area of two shoulders, the improved support can improve shouldersstress state, increase the strength of the surrounding rock in shear failure areaand enhance compressive capacity of roadway. Moreover, it can play the roleof support system and surrounding rock and ensure the roadway’s stability.