Test Study on Permeability Enhancement by Deep-hole Controlled Pre-splitting Blasting

The test study was made on the deep-hole controlled pre-splitting blasting technique in order to enhance the gas permeability of coal seam and improve the gas drainage rate.In this paper,the permeability enhancement mechanism and the effect investigation scheme by deep- hole controlled pre- splitting blasting were described,the site investigation and the comparison of the drainage effect by pre-splitting boreholes and ordinary boreholes along seam were conducted from the aspects of gas drainage quantity by one hole,the gas permeability coefficient of coal body near the hole,the gas flow per 100 m hole,the gas drainage rate per 100 m hole and the driving speed of the heading face.The results showed after the implementation of the deephole controlled pre-splitting blasting measure,the gas drainage quantity per hole increased markedly in the first 12 days,the gas permeability coefficient increased by 6.9 times,the gas flow per 100 m hole increased by 4.218 times,the gas drainage rate increased by 1.88 times and the driving speed of the heading face increased significantly.