Mining
- Created by: lucy
- Created on: 18-02-13 14:59
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- Mining
- Opencast coal mining
- Quarries or "open pits"
- Sides are dug at an angle and stepped
- Increase stability and prevent collapse
- Rock Type
- Weak, incompetant rocks like clay
- Shallow slope angles
- Weak, incompetant rocks like clay
- Structures
- Faults and joints
- Weaken the rock
- Rock bolts Wire netting Shotcrete Rock drains
- Weaken the rock
- Faults and joints
- Weathering
- Heavily weathered rock
- Weaker
- Shallow slope angles
- Weaker
- Heavily weathered rock
- Sides are dug at an angle and stepped
- Quarries or "open pits"
- Underground coal mining
- Longwall mining
- Shaft is dug from the surface, two roadways are driven out, shearer rotates to and fro the coalface, coal falls on conveyer belt, transported to shaft
- Roof is held up by hydraulic steel on chocks
- When coal is sliced, chock moves into new space
- Roof is held up by hydraulic steel on chocks
- Problems
- Faults displacing coal seam
- 1 or 2 m can disrupt production
- Damage shearer
- 1 or 2 m can disrupt production
- Folds and steep dips
- Longwall mining takes place horizontally
- Coal seams cannot dip at an angle greater than 5 degrees
- Longwall mining takes place horizontally
- Washouts
- river channel switching on the delta top
- Coal seam is lost as the peat is eroded away by the river
- In peats place is now conglomeratesand sanstones
- Coal seam is lost as the peat is eroded away by the river
- river channel switching on the delta top
- Seam splitting
- 1 thick coal seam splits into several thinner, uneconomic seams
- Result of different rates of subsidence in different parts of the delta
- 1 thick coal seam splits into several thinner, uneconomic seams
- Methane gas
- Flammable -> danger of explosions
- Faults displacing coal seam
- Shaft is dug from the surface, two roadways are driven out, shearer rotates to and fro the coalface, coal falls on conveyer belt, transported to shaft
- Longwall mining
- Aberfan 1966
- Long term -> Pore water pressure on saturated ground
- Trigger -> Heavy rain two days before
- Unconcolidated soil on top of town slid down mountain
- Trigger -> Heavy rain two days before
- 144 deaths
- Long term -> Pore water pressure on saturated ground
- Opencast coal mining
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