Stoping Methods of Mining
Stopes are the production centers of the mine. It is here that the ore is first broken. The safety of the miner is the paramount consideration in selecting a suitable mining method. Even then, miners must he constantly on their guard to make their workplace as safe as possible. Loose rock is a constant potential danger. As soon as a miner enters a stope, the back is examined carefully, and any loose material is brought down with a scaling bar.
A stope must also be designed so miners can reach their working places, remove the broken ore, and get supplies, tools, explosives and equipment in. It must also be properly and continuously ventilated, so that the air does not fill with dust and machine exhausts. In very deep mines, where the wall rocks can be very hot, ventilation also helps to keep the air temperature low enough for miners to work.
Stopes are started from the main levels in a mine. The first step of the operation is known as silting — cutting a drift across the top or bottom of the ore to be mined.
There are several ways to remove ore from a stope. The silt may consist of a timber structure placed in a section of a crosscut which has had a slice taken out of the back. This structure will include chutes for the removal of the broken ore from the stope to be developed above the crosscut. It will also include the beginnings of the manways which must be maintained for access and for services such as compressed air, water and electricity.
In other instances, a series of short raises or box holes are opened in the rock. These are excavated at short intervals along the drift, or in the footwall parallel to it.
Development work for some stoping methods calls for a rather elaborate system of box holes. This is required for the removal of ore from scraper drifts, which in turn are fed from drawpoints underlying stope which extends for some distance along strike. Development work for a stope often includes rib pillars (oriented at right angles to the strike) and sill pillars (oriented parallel to the strike) over the main haulage way. In any case, development work provides access, ore removal, service and supply to a stope.
In trackless mining, box holes and chutes are replaced with a system of drawpoints spaced equally along the footwall of the orebody. These are developed so that they break into the ore at the sill level.