Study on reasonable blasting times of air-cannon blasting in hydraulic flushing borehole to promote gas extraction

Abstract：Aiming at the reasonable blasting times in hydraulic flushing borehole with air-cannon blasting to increase coal permeability and promote gas extraction, the mechanism of the promoting gas extraction was studied.The deformation process of the coal mass around hydraulic flushing borehole while air-cannon blasting energy acted on was simulated with LS-DYNA under different blasting times of 0～50.The variation characteristics of crack development caused by hydraulic flushing with air-cannon blasting were investigated.With regression analysis, the function expression of the nonlinear gradual change law between the maximum fracture radius and the number of air-cannon blasting times was obtained.Through numerical simulation combined with field test, it was determined that 40 times of air-cannon blasting after hydraulic flushing was a reasonable number of the blasting, which had theoretical guiding significance for popularizing and applying this technology.

Keyword：hydraulic flushing borehole;air-cannon blasting;blasting times;increasing coal permeability and promoting gas extraction;LS-DYNA numerical simulation;