Vertical Crater Retreat Mining Method

With the development of drills capable of drilling large-diameter (15 cm) holes up to 60 meters (200 feet) in length, conventional blasthole stoping has been replaced in part by a more efficient stoping method.

Vertical crater retreat (VCR), also known as vertical retreat mining (VRM), reduces the cost of mining wide, steeply orebodies. The stope has a similar shape, but instead of small longholes drilled in fans, large blastholes are drilled vertically from a top sill to break through into a bottom sill on the sublevel below. This allows the ore to be broken into the bottom sublevel in successive horizontal slices using the same blasthole for each successive deck or blast. No slot raise is required.

Only the bottom of each hole is loaded for each successive blast. This breaks off a slice of ore from the bottom of the ore block, which falls into the drawpoint level below, where it can be mucked out. Mucking provides room in the stope for the next blast. Dilution is controlled by removing just enough ore to create a sufficient void for the following blast.

This mining method is particularly safe, because the miner does not enter the area where the ore is blasted. Drilling and loading are done from the top sill. The method also eliminates the need to support the ground in the stope after each blast. Mucking can be done using remote-controlled LHDs.