Study On Advance Pre-blasting For The High Section Of Top Coal In Steep And Thick Coal Seam

Top coal caving in steep and thick coal seam is an important means for constructing high efficient mine and fullly recoverying coal resources.Based on the complex mining conditions of steep and thick coal seam in JianGou coal mine Urumqi coal area,on-site investigation,theoretical and experimental analysis,field mining testing and monitoring and other methods are used,the technology of advance pre-blasting for the top coal caving in steep coal seam is carried out systematically.The results show that: in the mining process of horizontal section top coal caving in steep and coal seam,the law of top coal damage,deformation and failure is complex,which is easy to induce dynamic instability and disaster.The working face in steep and thick coal seam is short,the stress is concentration in horizontal section working face and closer to the rib line.Because of the wide range subsidence by the main roof failure,the scale of stress distribution becomes narrower,the peak pressure shifts to the face,which provides basis for quantitative determination of the distance advance support on site.By numerical calculation and analysis,the laws of stress distribution and change and flow in broken top coal are revealed,and the deformation zone in top coal is defined.Field monitoring shows that:starting from the rib line,the advance pre-blasting process is non-implementation at the 0~10m range along the forward direction;the protective measures such as end support is used in the range of advance pre-blasting,the control range of advance pre-blasting is 10.0~35.0m,the range for ahead support is 0~45.0m,which provides a quantitative basis for determining critical indicators of ahead pre-blasting.The technique of advance pre-blasting for top coal is proposed and implemented in the top coal caving face of steep coal seam,using the optical visual inspection deformation of top coal (plate) before and after blasting,the loose circle monitoring within roadway and top coal and stress monitoring and so on,the parameters of this technique are optimized,the outstanding contradiction thataffects the safety of mining is resolved,advance degrees,top coal fragmentation and recovery rate are improved,which achieves a safety mining.This research provieds a reference for mining steep and thick seam and other top coal caving face.