Question 13
- Mention six underground mining methods
- State the four unit operations in the production cycle of a mine
- Outline three conditions under which underground mining is preferred to open pit mining
This question was attempted by all the candidates. They were able to correctly answer 13 (a) but could only fairly answer 13 (b) and (c) as the responses to these two questions by the candidates is not in conformity with the marking scheme. The question requested the candidates to give the following points:
(a) Underground mining method
- Shrinkage stoping
- Longwall
- Room and Pillar
- Cut and fill
- Vertical Crater Retreat (VCR) or Vertical Retreat Mining (VRM)
- Sub-level stoping
- Sub-level open stoping
- Square set stoping
- Stull stoping
- Breast stoping
- Sub-level caving
- Block caving
- Sub-level caving
- Rill stoping
- Retreat mining
- Bench-and-fill stoping
(b) The four unit operations in the production cycle of a mine
(i). Drilling
(ii). Blasting
(iii). Loading
(iv). Hauling
(c) Preference of underground mining over open pit
- Cost of equipment is lower for underground mining
- Depth capacity which is limited for open pit
- Selectivity is better for underground mining
- Waste disposal. Which is a problem for open pit
- Environmental problem.