Study On Gas Drainage Technology Through Hydraulic Flushing In Up-hole To Improve Permeability

Based on related references,this paper mainly researched gas drainage technology by hydraulic flushing in up-hole to increase permeability of coal,through the subject of hydraulic flushing to improve permeability and enhance gas drainage effect of up-hole in BeiChen mine.First,through the analysis of hydraulic flushing coal broken theory and pressure relief and permeability increasing effect of coal around drill, studied coal breaking mechanism of water jet,influnce of coal structure on coal broken,change of stress distribution around drill and its impact on permeability of coal,and summarised that the crack simplifed the process of water jet broken coal,the occurrence of gas urged coal tensile failure and shear failure,and the better effect of hydraulic flushingjthe better pressure relief and more range of pressure around drill;second,after analysis the influence of punching nozzle technical parameters on hydraulic flushing construction and coal broken,designed hydraulic punching bit of81-coal and work out the best bit type and parameters matched with different obliquitous angles of drill through field test;third,analysised the mutual influnce of hydraulic flushing technical parameters such as punching pressure,nozzel water yield,space between borehole and drill pipe,drill pipe propulsion rate and rotation rate,et.And through field test catched the resonable parameter and found it was not permanent,reasonable ratio of each parameter is the key to success of hydraulic flushing construction;at last,this paper proposed negative pressure method to measure the influence radius of drainage after punching and got it successful application,provided technical support for gas drainage technical of hydraulic punching;and the investigation of gas drainage effect showed that coal permeability incresed nearly7times and the average concentration of gas extraction in one drill increased3times after hydraulic flushing and gas drainage,meanwhile,content of gas in coal become2.54m3/t,decresed67%;gas pressure become0.24MPa,decreased57%,and indicated that the technology had got perfect performs and had some value to promote application...