Question 1.
In relation to underground mining define:
a) Primary Development
b) Secondary Development
Give examples of each, using sketches where required.
Question 2.
Describe in detail with the aid of sketches, raise boring and ladder raising.
Question 3.
Sketch and briefly describe the mechanisms involved in the excavation of rock using any four of:
• A drag cutter
• A point attack cutter
• A disc cutter
• A roller cutter
• A button cutter
Question 4.
List the criteria that should be used when selecting the site for a shaft.
Question 5.
A Continuous Miner has the following specification:
• Cutter drum width = 3.2 m
• Drum diameter across the picks = 0.9 m
• Available drum torque (cutting) = 160 kN.m
• Maximum sump force = 170 kN
• Drum speed = 57 rpm
• No. of picks on cutting drum = 84
It is to be use to cut coal which has the following cutting properties:
• Specific cutting force per pick (new) = 37.5 N/mm
• Specific normal force per pick (new) = 20.0 N/mm
Estimate the performance of the continuous miner:
1. when equipped with all new picks; and
2. with picks in an average condition of wear
Hint: the maximum depth of cut that can be taken by the machine will be limited by the available thrust force.
Base your estimate of performance on cutting torque and potential instantaneous cutting rate.
Question 6.
Detail the unit operations within a conventional drill and blast shaft sinking operation including the shaft bottom operations as well as those undertaken on the sinking stage.
Question 7.
Whilst pilot hole drilling to site a 200m deep vertical shaft, a 40m layer of unconsolidated wet sandy material was encountered at a depth of 80m. The remainder of the ground was generally good.
List the options that may be available to tackle this problem and describe, with sketches where appropriate, two such options.
Question 8
A shaft is to be sunk to a depth of 900 m from surface. Geological investigation indicate that at a depth from surface of 600m there is a 300m thick water bearing sandstone layer. Describe in detail a method that can be used in this instance to avoid flooding the shaft.
Question 9.
The haulage level of a mine using transverse sub level open stoping is described below:
There are both footwall and hangingwall drives which are connected at the extremes outside of the orebody and at regular intervals along the ore body's 600m of strike length. The footwall drive is connected centrally to a downcast shaft and ventilation raises are positioned at each end of the ore body. The connections in ore are called draw point crosscuts and drawpoints are developed from these crosscuts into the undercut of the stope. Draw a plan view of this showing all details of the hangingwall and footwall development, ventilation system, drawpoint crosscuts and at least one set of drawpoints. To understand the system it may be useful to sketch a section of the system.
Question 10.
Calculate the direct unit cost of a 4.5 x 4.5 m drill and blast development in sandstone given the following:
Rock S.G 2.6
Labour cost $400/shift including on costs
Productivity 1.4m/shift
Rock bolts and mesh $55 per m2
supported
Depth drilled per round 4 m
Depth pulled per round 3.9 m
Overbreak 10%
Overall explosives cost average $10.40/kg
Materials cost excluding explosives and ground support $350/m
Jumbo drilling at $6.50/m drilled
Mucking and tramming $9.40/tonne
Detail any other required assumptions.
Question 11.
State reasons for the popularity of decline mining in modern operations. What factors need to be taken into account in deciding the cut off depth beyond which shaft operations should be used instead of decline access.
Question 12.
Compare critically the cycle of operations in drill and blast and mechanical mining operations.
Question 13.
Describe and compare the ventilation systems used in single entry development operations.
Question 14.
For the following mining methods describe the development needs and sequencing required within a production area:
• Rubber tyred block caving
• Sub level open stoping
• Vertical crater retreat mining
• Sub level caving
• Longwall coal mining (retreat or advance)
• Room and pillar
Question 15.
Describe a tunnel-boring machine in detail and cite examples of their use. Particular emphasis should be placed on the cycle of operations for such a machine.
Question 16.
Describe a mobile miner. What are the advantages of mechanised methods of tunnelling over drill and blast methods?
Question 17.
What parameters are used when determining the shape of shafts and the size of shafts?
Question 18.
Describe the steps one would take when tunnelling through areas where the potential for an inrush of water exists. Detail the methods can be applied to minimise the risk of an inrush in such circumstances.
Question 19
Draw a sketch showing the principal orthogonal forces that act on a pick while cutting rock. What is the relation, if any, between these principal forces and the slewing pressure and cutter head torque?
Question 20
Describe with the aid of a diagram a typical blast design for a rectangular tunnel. Particular emphasis should be placed on identifying the cut, easer, trimmer and lifting holes. Why in such a round where ANFO is used for the majority of the holes might a more water resistant product be used in the lifter holes?
Design Task 1 (25% of course total)
A new vertical shaft has been proposed to connect surface to proposed workings at a depth of 1000m below ground. The shaft is to be a mineral hoisting and ventilation shaft with the ability to act as an emergency egress and has a proposed circular shape of 6m diameter. The stratigraphy of the geological strata at the shaft site is as follows:
The purpose of the exercise is for students to develop a shaft sinking and lining strategy for the site. The expectation is for students to compile a report of their findings, the report should include:
1. Proposed excavation strategies
2. Timelines/project management for the project
3. Equipment and consumables used
4. Costing's ( a useful source is the AusIMM monograph ‘Cost estimation handbook')
5. lining design
6. sinking stage design
7. shaft fittings
Design Task 2
The following data refers to a horizontal tunnel to be driven by a Tunnel Boring Machine (TBM).
• Diameter of tunnel, i.e. size of TBM cutter head = 5.0 m
• UCS (mean) of rock strata = 60 MPa
• Shear strength (mean) of rock strata = 15 MPa
The TBM has the following specifications:
• Available axial thrust = 4.5 MN
• Available torque = 880 kN.m
• Rotational speed = 4.6 rpm
• Muck clearing capacity = 0.26 m3/rev
• Disc cutter diameter = 260 mm
• Disc spacing = 100 mm
• Disc edge angle = 35º
QUESTIONS
Determine, making and justifying assumptions as required, the following:
1. the maximum axial boring rate in units of m/hr
2. the total axial thrust requirement for the machine to meet this task (MN)
3. the total torque required (kN.m)
4. the rotary cutter head power required (kW)
5. the specific energy of the operation (MJ/m3)
Neglect any allowance for gauge cutters on the machine.