Vertical Crater Retreat

An underground mining method in which vertical longholes are drilled from drives developed in the ore between two levels. The ore is then blasted using a charge that occupies a relatively small length of the hole, some distance from the bottom face. The blast creates downward facing craters and the broken ore drawn from the stope on the lower level. The method has a low explosive consumption. Used at the Homestake mine in the United States.