METHOD OF FORMATION OF DEEP-HOLE CHARGE IN PERMAFROST Russian patent published in 1997 - IPC

FIELD: drilling and blasting operations in mineral deposits located in the permafrost zone. SUBSTANCE: the method consists in drilling of bore-hole 1 with overdrill 4 determined by relation . Then along the bore-hole axis in the area of location of the explosive pipe 2 with a blanked off end and holes 3 on the walls is installed; the diameter and arrangement of the holes is determined by the necessary shape of the explosive charge surface; heat-transfer agent is fed to the pipe under pressure for warming-up and removal of the defrosted layer of permafrost from the walls by settling in overdrill 4 up to formation of cavity 5 of the required shape and volume; then the pipe is removed from the bore-hole. The explosive charge is placed in formed in formed cavity 5 on the defrosted rock in overdrill 4, then an initiating charge is installed and stemming is tamped in the bore-hole. Hot air or steam may be used as a heat-transfer agent. EFFECT: higher efficiency.