Sub-Level Caving

An underground mining method used in large, steeply dipping orebodies where the wall rock is of an incompetent nature. Parallel drives are developed in the ore on equally spaced levels. The ore is then drilled and blasted using longholes between levels, often in a circular or fan pattern, on retreat. The weight of the rock is used to assist breakage. The upper levels are mined ahead of lower levels. Broken ore is extracted from the drive before the next blast takes place. The wall rock caves in when the ore is extracted.