(1) Design a coal overburden throw/cast blast for the following situation:
a) Blast length 900 m
b) Blasted bench width 100 m
c) Bench height 20 m
d) Overburden of shale/siltstone/sandy shale, average density 2.5 tonnes/m3
e) Standoff distance 1.5 m
f) Wet holes
g) Hole diameter 250 mm
Design the blast pattern, select initiation system, detail initiation sequence.
(2) Students are to undertake a tunnel blast design for the following conditions:
• Tunnel is 5.5m wide by 5.5.m high
• Rock is a sandstone with a UCS of 400 MPa
• Drill hole diameter is 51 mm, hole length is 4m
• The cut is to contain 2 relief holes of 75mm diameter
• Dry conditions are anticipated, ANFO to be used with a density of 800 kg/m3 and a powder factor of 0.6 kg/m3
• Nonel detonators are to be used
Students are to determine:
1. The design of the cut, including burden and spacing for each element of the cut.
2. Burden and spacing of the easer, perimeter and lifer holes
3. Stemming length required
4. Method of hole priming
5. Firing sequence timings for the holes
6. Explosive utilisation
Results should be presented in a report format, including diagram s as required and details of calculations undertaken.