Underground mining uses various techniques and methods to excavate minerals, metals and rocks. Depending on what is being mined, it can be called hard rock or soft rock mining. Some of these materials include, gold, diamonds, silver, copper, iron, zinc, lead, tin, coal and salt. An important part of this process is ventilation.
There will be hazardous gases and dust and of course, the equipment used can also emit carbon monoxide, so it is dangerous work. Ventilation helps to clear this and sometimes, in times of danger, ventilation shafts can be used for escape. Here are some of the techniques used in underground mining, as well as the state-of-the-art underground mining technology that is involved.
1. Cut & Fill
This method of short-hole mining is used in irregular and narrow ore zones. It can be difficult to use long-hole techniques due to the hanging wall. An access ramp is sent to the bottom so that the ore can be easily accessed. The ore is mined and filled with sand and waste rock and consolidated with concrete or left unconsolidated. This is quite an expensive method of mining but there is very little loss of ore.
2. Drift & Fill
This is a somewhat similar method to cut and fill. Cut and fill uses narrow and irregular ore zones whereas drift and fill uses wider ore zones. The initial drift is developed in the ore and backfilled with consolidated fill. The next drift is adjacent to the first. This is an ongoing process until the ore is mined to the full width. Then, the next cut is done on top of the first one.
3. Room & Pillar Mining
This method of mining is used for mining coal, though it can be used for other materials as well. It is considered to be one of the safest and eco-friendly methods of mining coal. There is very little movement of land and maintains clean water standards. Very large pillars of coal are used to help support the roof of the mine. This helps to maintain the integrity of the land.
A kind of grid is eventually formed (rooms). Coal is collected and cleared by being placed on a conveyor belt. These are eventually taken to a wash plant and the coal will have rock and debris removed. This cleansing method helps to remove sulphur and any other kind of minerals so that it can eventually be offered to customers.
4. Shrinkage Stope Mining
This is another short-hole mining method used for steeply dipping orebodies. The process actually mines upwards, from a lower to a higher level. This technique causes broken rock that fills the excavation, making it into a kind of platform, which, in effect, helps to stabilize and support the walls. This platform helps because it provides a stable way to work.
In some ways, it is similar to cut and fill as well. Not all the ore is removed though. Only a certain required amount is mined from the stope so that it enables drilling and blasting for the next slice.
There are still more mining methods used, depending on the specialty of the mining companies. It is expensive and hard work that uses declines or tunnels to get to the material. People and machinery have to be able to reach these locations, so it is not work for the fainthearted or someone with claustrophobia!