When it comes to mining systems there are four main types of mining that you will find involved. There is dredging, surface mining, underground mining, and insitu mining. All of these types of mining have their own mining systems that help them process whatever ore or natural materials the miners are after.
Dredging is a very high volume type of mining technique for lower valued products that are plentiful and near some sort of water source. They will use scoops or buckets to extract the materiel from shallow waters, often these can be man made lagoons. They can also do a higher tech variation of this by doing undersea mining where the material is sucked up from the sea floor. These types of mining systems are often combined with the processing being done on a floating barge which will most often be anchored in the middle of the water source or lagoon.
Surface mining, another one of the various mining systems used can be called Open-cast if they are mining soft rock like coal or limestone and called Open-pit if they are hard rock mining for copper or diamonds for example.
Surface mining generally will not go any deeper than 200 meters or around 656 feet below the surface and this is usually to extract cheaper metal from underground. The cut off point will actually depend upon the cost of the two methods. The surface cost will be dominated by the ore waste ratio and in turn it will depend upon the shape of the ore body, the amount of its overburden to be removed and the safe steepness of the wall.
Underground mining is mining through shafts or inclined roadways. There are usually two access routes one that is for the miners and their materials and then one is for the ore being mined. Also for safety and for ease of ventilation the fresh air will come in one shaft and then exhausted out the other as well.
Once the underground mine has reached the depth they want it becomes permanent so it is required that the roof supports be extremely strong. This will often include bolts into the rock to tie the layers together for more strength. There are also tunnels that go into the ore deposit itself and these are temporary structures and they require less support.
The two main extraction techniques used in underground mining are:
- Room and pillar – This is a matrix of excavated rooms with pillars that are left between them to hold up the roof. This is good for shallow mines where the mineral is thick but of low value.
- Lonewall systems – The minerals are extracted as a face between two parallel roadways. This is popular with coal mining by using shearers or plows.
- Block Caving – These are tunnels that are driven in under the ore deposits and the rock above is then fragmented and the rock will collapse under its own weight and the material can be drawn down through these ore passes.
- Cut and Fill – This is for irregular ore deposits of higher value minerals and involves mining up in horizontal slices and each slice back filled, usually with concrete to provide a good floor.
The fourth most common type of mining is Insitu mining. There are two main types, solution and thermal.
Solution is mining that involves injection of water down drill holes into soluble deposits, most commonly would be salt. Then the mineral solution is pumped back to the surface for processing.
The thermal is actually still in its research stage but theoretically it could be possible to burn coal insitu by making cracks and then injecting oxygen and a heat source and then recover the heat from this process. In other words it is like creating an underground power station without ever having to actually extract any of the coal.