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.

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.

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

Various rock-testing techniques are employed in rock mechanics. Students are to select a particular parameter that is useful in assigning a value to a particular variable employed in rock mechanics (e.g. shear strength, UCS etc) and to describe suitable techniques of evaluating this parameter. This is a research report and all sources used should be cited and referenced in an appropriate manner. The results should be presented in the form of a technical report and illustrated as appropriate. In particular students should present the methodology of testing as well as any flaws in the testing method.

Estimate the machines production under these conditions using the travel time curves given in the Caterpillar Performance handbook.

Attachment:- questions.pdf