- Created by: HannahCaviel
- Created on: 24-02-17 09:08
- Access tunnels are drilled into the coal
- The tunnel roofs are then supported by steel hoops
- The tunnels are then linked by a working face
- The working face roof is supported by hydraulic jacks
- The coal cutter then begins to extract coal from the working face
- The jacks are moved back to allow the cut coal to collapse to form goaf
- The coal cutter then moves to the next section of coal and the process repeats
Two access tunnels are drilled to create a vent for poisonous gases such as methane to disperse into the atmosphere. On top of this, it is necessary to have to access tunnels as if one collapses, there is still a second tunnel that can be used.
- Overlying soil is removed and placed on a separate pile
- Overburden (overlying rocks) are removed and placed in a waste pile
- Coal is extracted, with the thinner seam being extracted one at a time on the way down to the lowest seam.
- Seams that have been extracted are filled in by the overlying soil
- Once all of the coal is extracted, the overlying soil and overburden is replaced so that the environment returns to its normal state
- poisonous gases disperse into the atmosphere and are not trapped
- low use of technology so is relatively cheap
- is flexible and can move around problems
- no collapse as there is no roof
- water can be easily pumped out
- can be an eyesore for the environment
- can create dust and noise pollution
- cannot reach deep seams
- can cause disruption to groundwater supplies
Pillar and Stall
Pillar - where the coal is left to support the roof
Stall - the areas of coal that is extracted
Pillar and Stall mining is used when the area to be mined would be too invasive to mine using longwall mining. The mining must have no risk of subsidence as the area above is important. For example, the area of coal is underneath a town.
ADVANTAGES OF UNDERGROUND MINING
- Can reach much deeper seams that opencast mining
- Can mine underneath the sea
- Less polluting than opencast
- Waste can be backfilled into the mine
- Toxic gases such as methane, CO2 and Carbon Monoxide accumulate in the mine
- Noise and Dust pollution
- Risk of cave-ins and roof collapse
- Water can cause flooding and is hard to pump out
- use of high technology means it is expensive
The conditions needed for coal to form are, humid, equitorial climates, with anaerobic environments and large amounts of organic matter. The organic matter when it dies decomposes and is placed under heat and pressure to transform into peat.
Burial by sedimentary processes tranform the peat into coal by compaction, heat and pressure. The changes from Peat into Coal is called the coal series. the coal starts off as peat, then turns into ignite, then into bituminous coal, and then finally into anthracite. As the coal series increase, the density of the coal produced is higher, alongside the heat, pressure and depth of burial also increasing.
Problems which make Underground Mining more diffic
Faulting - Faulting can cause difficulty to underground mining as the equipment used needs to be constantly moved to reach the moved coal seams. This can be time wasting and also uneconomic.
Methane Gas - When accumulated, methane gas can be highly flammable. Therefore, it is a danger to the miners and the equiptment in the mine, and needs to be removed correctly. This can further increase the cost of mining and also takes more time.
Washouts- Washouts result from the river switching on the delta tops. Peat is eroded away by the river sands and so, the source of coal is lost
Sandstones - Sandstones are hard and permeable and may allow flooding into the mine
Seam Splitting - This is when the coal seams split from one large coal seam into several, thinner coal seams. This results from different rates of subsidence in the delta. This can make the mining process last longer and be more costly.