26. Determine the maximum production for a Caterpillar D11R Dozer fitted with a Universal Blade using the diagram below for a dozing distance of 60m.
Determine the corrected production for the dozer for downhill dozing on a 5% slope, with a 50 minute working hour and an average operator as per the correction factors below.
27.Normally the height of windrow is?
28.Which of the following has the lowest power consumption in kwh/m3
a. BWE
b. Electric Face shovel c. Walking dragline
d. BCE
29.Which of these would be considered an excessively steep a grade for a normal rear dump truck?
a. 4% b. 6% c. 8% d. 10%
30.Draw and label in detail a hydraulic excavator
31.Sketch a cross section of an open cut mine, label the major components, and explain briefly the purpose of each.
32.Sketch and label the four most common slope failure types.
33.Calculate the efficiency of a 24H Caterpillar grader maintaining a 40m wide haul road, given the following:
? road length is 16,500m
? machine takes 8 hours to complete the task ? average speed of the machine is 22km/hr
? task completion requires making 8 passes
34.Given are the following data for a shovel-truck surface mine operation:
??required production/bench = 16,000 tonnes/shift
??operating period = 1 shift/day
??material = well blasted rock
??working time = 51 min/hr and 10.5 hrs/shift
??operating factor = 83%
??specific weight of rock = 2.35 t/m3 Calculate the idealised output (m3/hr) of the shovel.
35.
a. What are the different types of haul roads in use in surface mining?
b. Design a spiral haul road system for the following surface mine:
i. pit consists of 6 benches
ii. bench height is taken as 12m=H
iii. crest-to-crest distance is 21m
iv. bench face angle is 59?
v. a haul road having a width of 30m and 8% (=G%) gradient will be added to the inside of the pit wall
36.If the width of a haul unit is 15m, determine the minimum width of a haul road for:
o Single lane haul road operation
o Two lane operation
o Three lane operation
37.Describe the various methods of truck loading using either a shovel or excavator fitted as a backhoe
38.Estimate the cycle time and production of a Caterpillar 777D flat floor off highway truck operating on a level haul road of 2000m length. The road is a rutted dirt roadway with no maintenance and no stabilisation, tyre penetration is 4 cm. The following can be assumed;
o Loading time 1.4 min
o Manoeuvre and dump time 0.8 min
o Truck hauls 40 tonnes of ore each trip o Job efficiency of 0.8
39.For the situation in question 38, determine the cycle time if road conditions were improved to a rolling resistance of 30 kg/tonne.
40.For the problem in question 38 and 39 the engineer at the site is considering the use of a shorter, 1000m, 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?
41)An off highway truck weighs 23 t empty and carts a payload of 35 t up an 8% grade. The RR factor is 40 kg/tonne. Calculate:
a) The total resistance (kg)
b) The effective grade (%)
42)A rubber tyred scraper unit weighing 50 t is towed by a crawler tractor weighing 40t up a 4% grade. The RR factor is 50kg/t. Calculate:
a) The rolling resistance (kg) b) The grade resistance (kg) c) The total resistance (kg)
43)A Caterpillar D30D articulated dump truck has the rim pull curve in figure 1. (Gross weight 21.9 t empty, 49.117 t loaded). If the truck ascends a 5% grade with a rolling resistance of 50kg/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)
Figure 1: CAT D30D Rimpull, Speed, Gradeability (Caterpillar Performance Handbook version 31 (2000)).
44)The average speed of an 18m3 scraper is 40 km/hr and its return speed uphill is 22 km/hr over a 400 m haul distance and a 450m return distance. Using a fixed time of 4 minutes, calculate the cycle time (min).
45) What are the advantages and disadvantages of in-pit crushing
46) 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.
Note: The Caterpillar and Komatsu Performance Handbooks are provided on the course Moodle page
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 (ie 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.
a. A pit with a straight ramp of 800m, with a gradient of 10%, supplies a ROM pad 1500m away via a level haul road all of loose gravel. Mining of a dipping ore body, with a specific weight of 2.5 t/m3, is required to be carried out at a rate of 10,000 tonnes/8 hour shift to feed the mill.
Since truck speed is restricted to 50kmph, assume the average speed of a truck during a round trip is 45kmph, including reversing to load. Waste material of specific weight = 1.85 t/m3 is also to be mined, and deposited on a waste dump 200m from the pit. The waste dump
already has a height of 10m, and an area of 100m x 60m from pre-stripped overburden. Excluding the overburden, the strip ratio is 1:4.5.
Other factors that are working assumptions are:
Availability of excavator 83%, Swell factor of 30%
Bucket fill factor of 88% Excavator cycle time 45 seconds
Rolling Resistance Factor (RRF) = 15 kg/t
Coefficient of Friction, µ = 0.25 Grade Resistance Factor = 20 kg/t
(i) Calculate required output by a single excavator appropriate to this production and select an appropriate machine.
(ii) Calculate cycle times for trucks.
(iii) Calculate number and size of trucks.
(iv) Ensure trucks are capable of carrying out this mining safely.
List and justify your assumptions.
3. Working Bench
Consider a mining sequence on a working bench.
a. Define the width of a working bench with a neat sketch.
b. Design a working bench when a single shovel of 6.8m3 capacity details of
which are supplied in the notes with single spotting is used: Given:
i. design bench height =15m
ii. shovel will move along one line parallel to the bench face
iii. bench face angle 65°
iv. parallel cut will be used with turn and back
v. single spotting
vi. haulage by 50 tonne capacity truck
vii. truck width = 5.5m
viii. truck tyre rolling radius = 1.2 m
ix. a safety berm is required
4. Pit Slope Angles.
Define, with a neat sketch, the different types of slope angles in a surface mine
Given:
- No. of benches = 9
- Bench face angle =69°
- Safety bench width = 10m
Based on the above data determine the following:
1. the overall slope angle
2. the overall slope angle if you introduce a ramp of 27 m width on the 5th bench
3. the inter-ramp angles
4. on the initial design, the overall slope angle if you introduce a working bench only on the 2nd bench
5. on the initial design, the overall slope angle if you introduce a ramp of 27 m width on the 7th bench
6. the inter-ramp angles
7. final slope angle at the end of pit limit
Assume bench height of 20m.
5) A Caterpillar 631 E tractor scraper has the following characteristics:
Maximum heaped volume = 19.6 Bm3
Maximum payload = 34,000 kg
The material hauled is earth with a density of 1825 kg/Bm3
Rolling resistance is 40 kg/t and operating conditions are average with a job efficiency of 45 min/hour.
The haul route comprises of the following sections:
Section 1 (100m) level-loading zone
Section 2 (800m) 5% down grade
Section 3 (100m) level dumping zone
Section 4 (1km) 6% up grade
Section 5 (80m) level turnaround area.
Estimate the machines production under these conditions using the travel time curves given in the Caterpillar Performance handbook.