1. Summarise the steps in the development of an open pit mine.
2. Define or describe the following terms
a. Bench height
b. Working bench
c. Crest
d. Cut
e. Toe
f. Safety bench/catch bench
g. Bench face angle
h. Back break
i. Berms
j. Bench floor
k. Angle of repose
l. Bench width
3. What are the purposes of safety benches? What is the width of a safety bench?
4. What is the width of a safety bench?
5. Discuss some of the aspects that enter into bench height selection
6. Draw a sequence of five benches. Label the crest, toe, bench face angle, bench width and bank width.
7. If the bench face angle is 65°, the bench width is 20m and the bench height is 12m determine the overall slope angle for a sequence of four benches.
8. Discuss the different aspects which must be considered when selecting the ore access location.
9. What is the difference between single and double spotting of trucks? Advantages? Disadvantages?
10. Using the data for the Caterpillar 777G haul truck given overleaf, answer the following questions:
a. Load distribution on the front and rear tyres loaded
b. Payload
c. Turning circle
11. In the design and construction of a mine haul road, what layers are involved? Describe each one starting at the lowest layer. Describe the considerations in determining layer thickness.
12. Suggest a haulage road width for two-way traffic involving Cat 777D trucks.
13. What is meant by the California Bearing ratio? How is it determined?
14. The following road cross-section dimensions apply at a particular mining operation which uses Komatsu 930 trucks:
a. Safety berm width 3.5 m
b. Tuck width 7.3 m
c. Space between trucks 5.0m
d. Width of drainage ditch 2.0m
e. Overall road width 25m
f. Bench face angle 75°
Draw the section. How well does this design correspond to the rules for two-way
traffic?
15. In the design of a straight haulage road segment, what major factors should be considered? What is the design rule for road width for single way traffic?
16. Define what is meant by:
a. Stripping ratio
b. Overall stripping ratio
c. Instantaneous stripping ratio
17. What is meant by the term push-back?
18. What is meant by the term cutoff grade?
19. What is meant by struck capacity? What is meant by heaped capacity? What controls how full the dipper is actually filled?
20. Define the following terms:
a. Bank weight
b. Loose weight
c. Swell
d. Percent swell
e. Swell factor
f. Fillability
g. Fill factor
21. What is the general rule of thumb concerning matching of shovel loaders and haulers?
22. What is meant by rimpull? What is meant by tractive effort?
23. Discuss the concept of rolling resistance.
24. Sometimes rolling resistance is expressed in terms of % and sometimes in terms of kg/tonne. If the rolling resistance is 60 kg/tonne, what would be the equivalent value in %?
25. What is meant by the grade resistance? What is meant by the term total resistance? If rolling resistance is 3% and the grade resistance is 8%, what is the total resistance assuming the truck is travelling up an upwards grade? What is the total resistance if the truck is travelling downhill? In each of these cases which of the performance or retarder curves would be used?
26. What is autonomous haulage?
27. A dragline is to be selected to remove overburden at a rate of 395,000 bank cubic metres per month. If the dragline is scheduled to operate 720 hours per month which an operating efficiency of 0.8, the bucket fill factor is 0.8 and its cycle time is 50 seconds, what should be the size of its bucket?
28. Define the idealised output of a power shovel
29. Draw a plan and cross-section of a dragline casting overburden from a new strip to an old strip in a coal mining stripping situation for a single seam and for a two seam operation.
30. Define the following terms:
a. Availability
b. Operational availability
c. Mechanical availability
d. Physical availability
e. Utilization
f. Working efficiency
g. Job efficiency
31. The total cost of ore mining at an open pit is $ 35per tonne and that for waste is $ 25 per tonne. If the value of the ore is $ 110 per tonne and the company requires a 10% profit margin, what is the maximum stripping ratio?
32. Differentiate between the following:
a. Scheduled hours
b. Annual hours
c. Total hours
d. Working hours
e. Shift hours
f. Operating hours
33. For a 77t truck with Gross Vehicle Weight (GVW) of 136078 kg with dual rear tyres and a tyre inflation pressure is 120 psi (or 8.43 kg/cm2). Use the equivalent single tyre loading.
i. Determine the contact surface area
ii. If the sub-grade material is a firm or stiff clay, then determine the minimum required distance between the wearing surface and the top of the sub-grade.
iii. With the same truck specifications, design an acceptable haul road (i.e. determine different thicknesses of different layers) using CBR method. Choose your own material for different layers with proper justifications. (Use the required conversion factors)
34. Dragline Output
i. A dragline with a 2 cu yd bucket working in wet, sticky clay, with a swell factor of 20%, handles an average loose volume of 1.8 cu yd. It can complete 3 cycles per 2 minutes. Calculate ideal output, based on digging at optimum depth with a 90°angle of swing, and no delays.
ii. Using the tables provided, calculate the probable output if the angle of swing is actually 120°and the depth of cut is 10ft.
35. Determine the loosening costs in the following situation: Machine D11R Tractor with No. 11 single shank ripper in coal Rip spacing 1600mm
Ripper penetration 500mm Rip distance 150m
Rip time 4.32 minutes Manoeuvre time 0.35 minutes
Seismic velocity 2500 m/s (assume this is a realistic value for coal, graphs available to check).
Working rate per hour $ 120
What is the effect of the seismic velocity of rock on dozer ripping operations?
36. A Motor grader will travel at an average speed of 9 km/hr along a haul road to clear the shoulder for a distance of 17.5 km on one side. It is expected that proper clearing will require four passes, and that the machine has the usual efficiency factor of 0.6. Calculate the production expected from this grader performing this task.
37. Determine the maximum production for a Caterpillar D10T Dozer fitted with a Semi - Universal Blade using the diagram below for a dozing distance of 90m.
Determine the corrected production for the dozer for downhill dozing on a 2% slope, with a 50 minute working hour and an average operator as per the correction factors below.
38. What is the difference between a shovel and an excavator?
39. Calculate the efficiency of a 24H Caterpillar grader maintaining a 40m wide haul road, given the following:
• road length is 5,000m
• machine takes 8 hours to complete the task
• average speed of the machine is 22km/hr
• task completion requires making 8 passes
40. Given are the following data for a shovel-truck surface mine operation:
• required production/bench = 15,000 tonnes/shift
• operating period = 1 shift/day
• material = well blasted rock
• working time = 10.5 hrs/shift
• operating factor = 83%
• specific weight of rock = 2.6 t/m3
• Calculate the idealised output (m3/hr) of the shovel.
41. Describe a bucket chain excavator. What cut methods can be used with a BCE?
42. Estimate the cycle time and production of a Caterpillar 777D flat floor off highway truck operating on a level haul road of 4000m length. The road is a rutted dirt roadway with no maintenance and no stabilisation, tyre penetration is 2.5 cm. The following can be assumed;
o Loading time 1.4 min
o Manoeuvre and dump time 0.8 min
o Truck hauls 80 tonnes of ore each trip
o Job efficiency of 0.8
43. For the situation in question 42, determine the cycle time if road conditions were improved to a rolling resistance of 20 kg/tonne.
44. For the problem in question 42 and 43 the engineer at the site is considering the use of a shorter, 2,200m, haul road that has a slope of 6% adverse. If all other factors remain the same which haul route should be selected on the basis of shortest cycle times? What are the cycle times and hourly productions?
45. An off highway truck weighs 23 t empty and carts a payload of 35 t up a 4% grade. The RR factor is 40 kg/tonne. Calculate:
a) The total resistance (kg)
b) The effective grade (%)
46. A rubber tyred scraper unit weighing 50 t is towed by a crawler tractor weighing 40t up a 6% grade. The RR factor is 40kg/t. Calculate:
a) The rolling resistance (kg)
b) The grade resistance (kg)
c) The total resistance (kg)
47. A Caterpillar D30D articulated dump truck has the rim pull curve in the figure below. (Gross weight 21.9 t empty, 49.117 t loaded). If the truck ascends a 5% grade with a rolling resistance of 40kg/t, find the following:
a) Total resistance (kg)
b) The required rim pull (kg) when loaded
c) The maximum speed of the truck when loaded (km/h)
48. The average speed of an 18m3 scraper is 37 km/hr and its return speed uphill is 16 km/hr over a 1000 m haul distance and a 1000m return distance. Using a fixed time of 4 minutes, calculate the cycle time (min).
49. What are the advantages and disadvantages of in-pit crushing
50. Continuous surface miners such as the Wirtgen surface miners are used at a number of operations worldwide. Describe such a machine and detail the type of operation where such a machine has advantages over traditional surface mining techniques.
Attachment:- Assignments.pd