Design Task 1 (25% of course total)
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.
Note: students should list any assumptions made.
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.