A mine is blasting with the following parameters:
Burden 5.8 m
Spacing 6.4 m
Stemming 2.9 m
Bench height 13.0 m
Sub-drill 1.2 m
Hole diameter 165 mm
Explosive P 700
Explosive density 1.18 g/cc
Explosive RBS 157
Rock factor 7
a) Calculate the mean fragmentation size using Kuz Ram (m)
b) The mine wants to change the hole diameter to 229 mm and needs a new drilling pattern that will not result in coarser fragmentation. For this exercise you can assume homogenous geology and no adverse effects due to geological structure.
Following a successful takeover of a neighbouring mining operation, the Mine Manager asks you to provide a design to change the explosive from Anfex to P700 as supplied to his current mine. You visit the "new" operation and observe the following:
Burden 4.1 m
Spacing 4.8 m
Stemming 2.5 m
Bench height 10.0 m
Sub-drill 0.9 m
Hole diameter 127 mm
Explosive Anfex
Explosive density 0.80 g/cc
Explosive RBS 100
Rock factor 7
As the load and haul operations are operating well above the industry norm, the Manager does not want any change in the blast result.
c) Calculate the new blast design.
2:A surface quarrying operation has been using a single capped fuse to initiate all blasts. Following a near miss incident when someone from a local village, taking a short cut through the mine, had passed a blast after the fuse had been lit, you recommend that they consider the use of electric detonators.
With reference to safety and concentrating only on those safety aspects unique to the use of electric detonators, what factors will you cover in your discussions with the mine on the use of an electric detonator to initiate future blasts?
3:An underground gold mine has asked for your advice on the best way to initiate pneumatically loaded Anfex in 38 mm diameter jackhammer holes in a narrow reef stope. The possible options being considered by the Mine Manager are:
a) Direct priming with an 6D Capped Fuse
b) A 6D Capped Fuse plus a Powergel 813 25 × 200 mm cartridge
c) Direct priming with a 8D Capped Fuse
He wants a trial, including a fragmentation analysis, to evaluate all three possible options. Describe what you would need to consider, e.g. trial location, how you would propose to conduct, measure and evaluate the trial.