Reference no: EM132384517
ENGIN2503 Surface Mining Operations and Equipment Assignment Questions -
1. Explain the terms
- Bench and overall slope angles
- Overall, breakeven and immediate stripping ratios, with reference to the open pit mining method.
- Mineral resource and Ore reserve
- Cut-off grade
- Powder factor
- Charge density
2. An open pit mine employs ANFO at a density of 0.8 g/cc as its explosive. Given the following details, determine the blasthole spacing.
- Blastholes are vertical and bench height is 12m.
- Burden and spacing of blastholes are the same, i.e. B = S.
- The specific gravity of the rock is 2.5.
- The powder factor is 0.5 kg of explosive per m3 of rock.
- Hole diameter is 225 mm.
- Stemming column length is 3 m and subdrill is 2m.
If ANFO has a cost of $1050 per tonne, what will be the cost of explosives per tonne of rock?
3. Explain various deciding factors related to choice of surface mining over underground mining methods.
4. Discuss the concept of stripping ratio and how haul road gradient, bench, stack and overall slope angles affect it.
5. Illustrate with a suitable diagram, how waste overburden and orebody geometry dictates the choice of surface mining method.
6. What is meant by "break-even stripping ratio" and what factors would you consider when you need to determine its value?
7. What is difference in opencast, open pit and quarry mining?
8. Briefly describe frontal cut, drive-by and stop-and-reverse parallel operations.
9. Explain the following terms with the aid of sketches, as they apply to an open-pit operation;
(a) Overall slope angle
(b) Bench stack slope angle
10. Why is the individual bench slope angle steeper than the stack slope angle, which is steeper than the overall pit slope angle?
11. A dragline is to be selected to remove overburden at a rate of 395,000 cubic meters per month. If it will be scheduled to operate 720 hours per month with an operating efficiency of 0.80, its bucket factor is 0.85 and its cycle time is 54 seconds, what should be the size of its bucket?
12. Describe briefly how the operational life of a mine can influence the choice of transport equipment. Refer in your answer to a new open-pit mine and a deep open-pit mine that is near the end of its production lifetime.
13. Briefly describe the applications of the below equipments in surface mining. What are the major factors affecting the selection?
(a) Mining shovel,
(b) Dragline
(c) Bucket wheel excavator
(d) In-pit crusher
(e) Rail haulage
(f) Truck
(g) Conveyor belt
14. Explain the importance of slope angle in economics of surface mines by some example.
15. A discontinuity is found fully developed from the toe to the bench surface on a 20 m high slope, slope angle 63o. The discontinuity (frictional angle 32o and cohesion 20 kN/m2) is planar and its strike is parallel to the slope face with a dip 42°. Determine the factor of safety in case of a planar slope failure assuming drained conditions. Unit weight of the rock is 2.7 t/m3.
16. Illustrate bench width. Why should we provide safety bench? What are the factors affecting the width of safety bench?
17. What is pit limit? Describe a procedure to determine pit limits.
18. Estimate the unit profit in mining and processing a 0.80% copper ore deposit if the selling price of copper in concentrate is $1.73/kg and overall unit costs are $6.5/ton. Overall recovery is 82%. Calculate the cut-off grade of the copper deposit.
19. A surface mine operators needs to purchase a front-end loader that will be used to load ripped coal onto on-highway dump trucks. The mine operates two 7 hour shifts per day, 5 days per week, and 50 weeks per year. The daily production of coal is 1500 tons. The desired cycle time is 1.0 min or less. The density of loose coal is approximately 1.0 t/m3. Assume that the load factor is 0.65, the bucket factor is 1.23 and the operating factor is 0.75. What bucket size is required?
20. Assume an underground mining cost of $25.5/ton ore for an orebody. Assume open pit mining costs at $0.0028/kg ore removal and $0.0035/kg waste removal. Determine the stripping ratio for an open operation that results in break-even cost differential between the two mining methods.
21. What is the purpose of pit limit optimisation and typical computerised optimisation methods?
22. What are typical mine wastes? Describe measures to safely contain mine wastes.
23. Briefly describe:
a) Objectives of production planning;
b) Taylor's mine life rule;
c) Sequencing by nested pits;
d) Production scheduling.