Long-hole drilling

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Term	Definition
Long-hole drilling	Procedure of drilling long holes to contain powder for breaking the rock in underground excavation. As an illustration, a tunnel may be excavated by first driving a pilot drift near the center of the tunnel. Then approximately 10 ft lengths of this drift are enlarged to full tunnel dimensions at intervals of 100 to 200 ft. THese excavated areas are used as working chambers to drill holes in the remaining rock to the next enlarged section. Holes are then loaded and exploded, with relief for the explosion provided by the pilot drift.

Term

Definition

Procedure of drilling long holes to contain powder for breaking the rock in underground excavation. As an illustration, a tunnel may be excavated by first driving a pilot drift near the center of the tunnel. Then approximately 10 ft lengths of this drift are enlarged to full tunnel dimensions at intervals of 100 to 200 ft. THese excavated areas are used as working chambers to drill holes in the remaining rock to the next enlarged section. Holes are then loaded and exploded, with relief for the explosion provided by the pilot drift.