Want to learn more about how coal gets from the mine to your home? We discuss the traditional and modern-day techniques and what else is involved in the process.
Traditional Coal Mining
Coal was originally mined by picking lumps off where the seam came to the surface. These formed outcrops and were typically found on hillsides. These coal stocks close to the surface were quickly exhausted, resulting in the ‘Bell Mine’ technique being developed. Sunken chambers were used to reach the buried material and consisted of a long shaft into the coal; from this platform, workers would begin mining by running outwards with picks. Due to the lack of support structure, workers progressively removed coal from around the shaft, it became unstable with collapsing roofs and sides. Once this occurred, the mine was abandoned, and another started in a nearby location.
Modern Day Techniques
Modern-day mining takes a much safer approach than its riskier predecessors, with coal now extracted through two main methods, open cast or surface mining and underground mining. Open cast mining is designed to extract coal which resides close to the surface and involves the removal of overburden to reach the coal. This overburden is stored until needed again when the open area is redeveloped with parks and recreational areas. This regeneration process restores the area where the open mining has taken place.
Underground mining can take the form of two main techniques, room and pillar and longwall. Underground mining is beneficial because it has a small impact on the surface with a limited area. Spoils are usually left in the mine, reducing this impact further. Typically underground mining is more expensive because of the greater machinery required to dig and establish the mines underground. Safety procedures are also essential to ensure the protection of all workers.
The most widespread and popular method is room and pillar. This involves ‘pillars’ of coal remaining un-mined and acting as strong supports in the different chambers with the product around them being excavated. This reduces the percentage of coal excavated but increases safety for the workers. It is a careful balance between having a sufficient number of pillars to support the cavity whilst not wasting the coal. Typically, 60% of the mine is extracted this way but can vary depending on ground and roof conditions.
Longwall Mining is the second most popularly method. A long wall of exposed coal, usually 150 – 200 metres, is mined in a single process with a machine slowly advancing, excavating the material. As this advances, hydraulic jacks are placed to support the roof providing a stable, safe working environment for workers. This method typically recovers 80% of the coal as pillars are not needed to support the roof. As the machine continues through the coal seam, the mine roof is allowed to controllably collapse behind, leaving the ground as if no one had been there.
