1. 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)
2. 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.
Table 5.2: Ideal Output of Short-boom Draglines in Cubic Yards per Hour Bank Measure
|
Class of material
|
Size of bucket (cu yd)
|
|
3/8
|
1/2
|
3/4
|
1
|
1¼
|
1½
|
1¾
|
2
|
2½
|
|
Moist loam or light sandy clay
|
5.0
|
5.5
|
6.0
|
6.6
|
7.0
|
7.4
|
7.7
|
8.0
|
8.5
|
|
|
70
|
95
|
130
|
160
|
195
|
220
|
245
|
265
|
305
|
|
Sand and gravel
|
5.0
|
5.5
|
6.0
|
6.6
|
7.0
|
7.4
|
7.7
|
8.0
|
8.5
|
|
|
65
|
90
|
125
|
155
|
185
|
210
|
235
|
255
|
295
|
|
Good common earth
|
6.0
|
6.7
|
7.4
|
8.0
|
8.5
|
9.0
|
9.5
|
9.9
|
10.5
|
|
|
55
|
75
|
105
|
135
|
165
|
190
|
210
|
230
|
265
|
|
Hard ,tough clay
|
7.3
|
8.0
|
8.7
|
9.3
|
10.0
|
10.7
|
11.3
|
11.8
|
12.3
|
|
|
35
|
55
|
90
|
110
|
135
|
160
|
150
|
195
|
230
|
|
Wet, sticky clay
|
7.3
|
8.0
|
8.7
|
9.3
|
10.0
|
10.7
|
11.3
|
11.8
|
12.3
|
|
|
20
|
30
|
55
|
75
|
95
|
110
|
130
|
145
|
175
|
Table 5.3:The Effect of the Depth of Cut and Angle of Swing on the Output of Draglines
|
Per cent of optimum depth
|
Angle of swing (deg.)
|
|
30
|
45
|
60
|
75
|
90
|
120
|
150
|
180
|
|
20
|
1.06
|
0.99
|
0.94
|
0.90
|
0.87
|
0.81
|
0.75
|
0.70
|
|
40
|
1.17
|
1.08
|
1.02
|
0.97
|
0.93
|
0.85
|
0.78
|
0.72
|
|
60
|
1.24
|
1.13
|
1.06
|
1.01
|
0.97
|
0.88
|
0.80
|
0.74
|
|
80
|
1.29
|
1.17
|
1.09
|
1.04
|
0.99
|
0.90
|
0.82
|
0.76
|
|
100
|
1.32
|
1.19
|
1.11
|
1.05
|
1.00
|
0.91
|
0.83
|
0.77
|
|
120
|
1.29
|
1.17
|
1.09
|
1.03
|
0.985
|
0.90
|
0.82
|
0.76
|
|
140
|
1.25
|
1.14
|
1.06
|
1.00
|
0.96
|
0.88
|
0.81
|
0.75
|
|
160
|
1.20
|
1.10
|
1.02
|
0.97
|
0.93
|
0.85
|
0.79
|
0.73
|
|
180
|
1.15
|
1.05
|
0.98
|
0.94
|
0.90
|
0.82
|
0.76
|
0.71
|
|
200
|
1.10
|
1.00
|
0.94
|
0.90
|
0.87
|
0.79
|
0.73
|
0.69
|
3. 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?
4. 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.
5. 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.
6. What is the difference between a shovel and an excavator?
7. 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
8. 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.
9. Describe a bucket chain excavator. What cut methods can be used with a BCE?
10. 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
11. For the situation in question 10, determine the cycle time if road conditions were improved to a rolling resistance of 20 kg/tonne.
12. For the problem in question 10 and 11 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?
13. 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 (%)
14. 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)
15. 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)
16. 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).
17. What are the advantages and disadvantages of in-pit crushing
18. 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.