Research on antireflection by hydraulic flushing in hole of cross-layer borehole and comprehensive testing method for effective extraction radius

To clarify the effective radius of hydraulic flushing in hole of cross - layer borehole in No. 3 coal seam of Changping Company, a comprehensive research method combining pressure drop method, tracer gas method and numerical simulation method was adopted. Based on the same borehole layout and testing environment,the scientificity and rationality of the effective extraction radius of cross - layer borehole were comprehensively analyzed. The engineering test method was used to compare and inspect the extraction effect of cross - layer borehole at different spacing. The results indicate that by using the method of hydraulic flushing in hole of cross-layer borehole,the effective extraction radius reaches 3. 5 m when the extraction time is 180 d. The total extraction amount of 7. 0 m hole spacing is 1. 1 times,1. 07 times and 1. 28 times of 5. 0 m,6. 0 m and 8. 0 m respectively,and good engineering practice results have been achieved. The comprehensive research method is accurate and reliable.