Posted: June 5th, 2015
Topic: drilling and blasting of rock
(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:
- The design of the cut, including burden and spacing for each element of the cut.
- Burden and spacing of the easer, perimeter and lifer holes
- Stemming length required
- Method of hole priming
- Firing sequence timings for the holes
- Explosive utilisation
Results should be presented in a report format, including diagram s as required and details of calculations undertaken.
(3)
Work Site Report:
For the site at which you work compile a report on the production drilling and blasting operations at your site. Points to include within your report include:
- The main methods of production drilling and blasting at the mine including machinery details.
- Production drilling geometry including hole sizes, drill patterns, etc.
- Types of explosives and primers
- Details of initiation systems and methods
- Performance in terms of powder factors, costs and general comments on efficiencies
- General observations on drilling and blasting
As a guide your report should be typed and be 5 pages of A4 excluding diagrams and appendices. To complete the report brief sections on location, geology, etc. can be included but please do not over pad.