Test of Shaped Charge Blasting with Slit Cartridge Water Interval Charge in Tunnel Peripheral Hole
The excavation of Grade IV surrounding rock of Mengsheng Tunnel is carried out by contin-uous charging blasting at the bottom of the hole,which has obvious over-excavation and under-excavation phenomenon.In order to ensure one-time blasting forming and reduce the disturbance of blasting to sur-rounding rock and supporting structure,the slit cartridge water interval charging technology is applied in the peripheral holes of Mengzhou tunnel,and field tests are carried out.The test results show that compared with the traditional smooth blasting,the water interval charge shaped blasting technology not only effectively controls the overcut and undercut excavation,but also forms a flat contour line,and the charge amount of the single hole in the peripheral hole is reduced by 25%,the hole distance is increased by 100～300 mm,and the half-hole rate of the peripheral hole is greater than 70%,which saves the initial spray amount of concrete and avoids the undercut shot.The frequent blasting disturbance to surrounding rock is reduced.
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