Underground mining occurs when there are rocks and minerals too far underground to reach by means of surface mining. The extraction via underground mining methods are to be done safely, economically and with as little waste as possible. The entry from the surface to an underground mine may be through a horizontal or vertical tunnel, known as an adit, shaft or decline.

Types of Underground Mining

Borehole Mining: It can be used in open pit mining which is a kind of surface mining.

Borehole Mining process:

• A hole is drilled deep enough into the ground to reach the rocks and minerals
• A long, tube-like tool (with sections for water to be forced down and pushed up) is dropped into the hole
• Water is forced down the tube forcing it to break dirt and rock in its way, on impact
• The combination of water, dirt, rock and minerals is called a slurry, which is pumbed back to the surface and stored
  
• The slurry is pumped back up to the surface where it is put into a storage tank
• The water is drained and the ore is taken out of it
• From that time on, the ore is treated depending on what it will be used for

Drift Mining

This kind of mining is done when the rock or mineral is on the side of a mountain. As far as possible, the opening to the mine will be dug below the rock or mineral vein. This makes it easier to extract the materials due to help from gravity.  Cool, hey? 🙂 The tunnels that are dug are horizontal and are called drifts.

Hard Rock Mining

With hard rock mining an opening is made that is called an adit. Tunnels, called shafts, into the ground are dug, blasted with dynamite, or drilled out. Shafts are dug vertically into the ground and each shaft has its own specific purpose, i.e. one shaft might be for miners to commute in and out of the mine; another shaft for transporting of mine machinery; another shaft is used for air or ventilation; etc.

The tunnels in a hard rock mine are divided into rooms with rock pillars.

Shaft Mining

South Africa has narrow but extensive gold reefs which slope at an angle underneath the ground. This means that some deposits are very deep underground and often difficult to reach. Shaft mining is needed to reach the gold ore.

The shaft mine has a vertical manshaft, a tunnel where mine workers travel up and down in an elevator. Equipment is also transported into the mine using this shaft. Short tunnels to the ore are dug from that manshaft.

After the initial drilling, blasting and equipping of a mine shaft, tunnels are built leading outwards from the main shaft so that the gold reef can be reached. Shaft mining is a dangerous operation, and roof supports are needed so that the rock does not collapse. In addition the intense heat and high pressure below the surface make shaft mining very complex, dangerous and expensive. There is usually an airshaft that gives the mine ventilation.

Slope Mining

With slope mining, the coal or mineral bed is located very deep and parallel to the ground. It is called a slope mine because the shafts are slanted. This kind of mining is done when there would be problems drilling shafts straight down.[/box]

Base metals are the common and inexpensive metals that are not considered precious. Examples of base metals are copper, tin and zinc.