RE: Mining Box cut and portal11 Mar 2021 15:37
Hi Hydrogen
I found this bit
"In soft rock, especially in the ASM sector, tunnels may be dug by hand, but in the majority of mines they are excavated by drilling and blasting. Tunnels may be drilled using hand-held machines called jackhammers, typically advancing 2m for each round drilled and blasted. The tunnel size limits the advance; generally, the round drilled cannot exceed the longest dimension (width or height) of the tunnel. They may also be drilled with mobile drill rigs which are usually electro-hydraulic. These machines may be single-boom, twin-boom or multi-boom and are often capable of drilling several development ends in a single shift. Advances typically range from 3m to 6m per round.
The development cycle normally involves drilling and blasting a round on one shift, lashing, i.e. cleaning out broken rock, and installing services such as pipes, tracks and ventilation equipment on another, the same day. After blasting, the usual re-entry period is four hours before personnel may return to the face, after ventilation has removed gases and dust. In ASM, lashing is often done with hand shovels, whilst larger mines use track-mounted or trackless mechanical loaders."
https://www.extractiveshub.org/topic/view/id/40/chapterId/292