Coal Mining Techniques and Problems

Read the Information Sheet and complete the table:

Question / Answer
1. / Describe open cast mining /
  • Surface
  • Overburden is rocks removed to depth of coal seam – can be expensive to remove
  • Spoil heaps are overburden near edge of pit
  • Restoration by backfill of pit
  • Pit dug at angle – weak rocks = shallower slope; faults and joints weaken rock and need improvement

2. / Describe longwall mining. /
  • Underground
  • Main shaft dug from surface
  • Ventilation shaft required
  • Coalface between two roadways
  • Rotating machine cuts coal from face, which falls onto conveyor belt
  • Held up by steel supports (chocks)
  • Mining is backwards – mined-out area allowed to collapse

3. / What are the main disadvantages of underground mining? /
  • Faults displace seam
  • Meet hard rock = machine damage
  • Fault = weakness = permeability and flooding
  • Horizontal so if dipping seams = can’t do

4. / What is washout? /
  • Change in sedimentation as peat eroded away by river, leaving sand and gravels instead of coal seam

5. / What is seam splitting? /
  • Splits into several uneconomical seams

6. / How does the water table affect mining? /
  • Flooding
  • Expensive to pump out water

7. / Why is methane gas a problem? /
  • Builds up and can be explosive

Opencast Mining / Underground Mining
Advantages / Disadvantages / Advantages / Disadvantages
Cheap – low tech / Can’t reach deep seams / Reach deeper seams than open / Expensive – high tech
Flexible if problems / Overburden storage instability / Mine under sea or areas where open pits would be eyesores / Inflexible if problems
Mine steeply dip seam / Groundwater supply disruption / Less polluting / Only mine horizontal seams
Economically mine thinner seams / Eyesore / Waste backfilled into mine / Water issues – expensive to pump out
Gas dispersed to air / Dust and noise (baffle) / Roof collapse/cave ins
Roof collapse less problematic / Less safe
Safer / Spoil tips unstable
Water easily dealt with

Coal Mining Techniques and Problems

Read the Information Sheet and complete the table:

Question / Answer
1. / Describe open cast mining
2. / Describe longwall mining.
3. / What are the main disadvantages of underground mining?
4. / What is washout?
5. / What is seam splitting?
6. / How does the water table affect mining?
7. / Why is methane gas a problem?
Opencast Mining / Underground Mining
Advantages / Disadvantages / Advantages / Disadvantages