Optimization of Goaf Gas Drainage Parameters Based on Studying Cracks in Overlying Strata of Stope

In order to obtain a good result of gas drainage in gob roof,the control methods of gas from goaf are discussed.Aiming at problems of unstable effect of gas drainage from high level strike inclined hole,low utilization rate of borehole,and frequent gas exceeding limits in passing through drilling field,we proposed a new method of using high level strike hole which is nearly horizontal to take the place of high level strike inclined hole for gas drainage.By means of similarity material simulation,theoretical analysis of key strata,and the software RFPA2D simulation,we analyzed the characteristics of the gob roof cracks,their variation,faulting,and bed separation rule to locate the position of cracks in overlying strata and to circle the gas enriched area so as to determine necessary parameters such as drilling field height,interval between drilling fields,and optimum position of boreholes,etc,to provide a theoretical basis for designing high level gas drainage hole in goaf.