Mining techniques make it possible to assess deposits and extract coal from them. As a reminder, coal is a fossil fuel of organic origin, originating from the decomposition of plants buried in the form of sediments more than 300 million years ago.
Deposits are generally deep areas where large amounts of coal are found. Wells must be drilled to access and extract the ore. When coal reserves are relatively close to the earth’s surface, surface mining can be carried out. There are also coal deposits under the oceans, currently untapped.
Before exploiting the coal deposits, it is necessary to evaluate them in order to put in place the appropriate extraction and exploitation techniques. The coal layers (called veins) are not always continuous and can form several strata hundreds of meters deep. The role of coal mining engineering is to understand the structure of these layers and to develop the best method for reaching and exploiting them.
Mining techniques come in two phases.
Upstream: the evaluation of deposits
It is first necessary to estimate a deposit in order to determine its volume, its quality, its profitability and the geological nature of the surrounding soils. The soil is probed to obtain information on the deposit such as the depth of the layers or the existence of faults. Through this prospecting, engineers can design the mine plan and the techniques to be used. This work makes it possible to know whether the operation is economically viable in the face of the investments to be made. An industrial center is then created around the deposit, explosives are used, wells and galleries are dug to prepare access to the coal seams.
Depending on the depth of the deposit, there are two types of mining operations:
To reach the coal layers, it is necessary to dig in the basement and build galleries. The place where the coal is located is called the “deposit”. The rolling galleries (3 meters by 3 meters) allowing the circulation of the wagons. They stretch for miles. Certain sizes (galleries between the upper and lower galleries), sometimes wooded, may not exceed one meter in height. The miners work there lying down.