Briefly describe the mechanisms involved in the excavation

Question

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, any two methods of 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.

What parameters are used when determining the shape of shafts and the size of shafts?

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 20m 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 1100 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 $25 per m² supported

Depth drilled per round 3.6 m

Depth pulled per round 3.6 m

Overbreak 10%

Overall explosives cost average $2.40/kg

Materials cost excluding explosives and ground support $150/m

Jumbo drilling at $3.50/m drilled

Mucking and tramming $3.40/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 two of 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 the methods of mechanised tunnelling available. What are the advantages of mechanised methods of tunnelling over drill and blast methods?

Question 17.

Occupational health and safety is the primary criterion used in designing and undertaking mine development. Discuss this statement.

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

A 6 m diameter TBM has been selected to undertake a tunnelling operation. It is to operate at 4 rpm with a cutter head power of 750 kW in medium strength rock. Determine the predicted machine excavation rate using the nomograph presented in the notes.

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?

Question 21

What type of loading arrangements may be found on a roadheader?

Question 22

A new vertical shaft has been proposed to connect surface to existing workings at a depth of 1000m below ground. The shaft is to be a mineral hoisting 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:

Depth from surface	Strata type
0-20m	Soil/overburden
20-100m	Weak regolith
100-300m	Siltstone of moderate strength low water flow
300-400m	Impermeable shale of moderate strength
400-800m	Bunter sandstone of high strength, aquifer, high water flow
800-1000m	Shales, medium strength, low water flow

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

and any other salient points.

Question 23

Students are to design a suitable ore pass to transport ore a vertical distance of 200m from  the extraction level to the transport level of a block caving mining operation. The proposed maximum lump size for the operation has an equivalent circular diameter of 500mm. The ore material will contain fines and there is a possibility of clayey materials. The ore pass will be developed in a high strength metamorphosed rock mass. Key elements should include:

1. Ore pass diameter

2. Lining materials

3. Dealing with oversize material

4. Delivery arrangements at the base of the ore pass (the ore is delivered onto a 54 inch cable belt conveyor)