SPECIALISED BLASTING
By Mutale Chipoma- Explosives Engineer
Wealth
Unearthed
BRIDGE ACROSS LUAPULA RIVER
BACKGROUND
•AEL invited to conduct blasting under water across
the Luapula river
•A total of 8 points under water for the construction
of abutment pillars were blasted.
•The areas to be blasted were surrounded by sheets
of steel to keep the water from flowing through.
BLAST DESIGN
•The first area to be blasted was 16m x 16m.
•Drilling was achieved by pneumatic drills with hole
diameters of 45mm
•A walk-way 1m wide was to be left around the blasted
area to be used during construction
•Holes drilled at 1m burden and spacing
•Perimeter holes drilled at 0.5m around the blast area
•Hole depth of 1.5m
CHOICE OF EXPLOSIVES
•The rock at the river bed was classified as medium to soft
material and powder factor was selected on this basis
•A technical powder factor of 0.39 kg/m3 was selected
•A water-proof explosive was needed because blast holes
were in water
•Magnum bustergel 32 x 200 was selected
CHOICE OF EXPLOSIVES CONT’ND
•Uncharged collar of 0.5m was left in the main
blast holes
•Holes charged with five cartridges
•Two cartridges tied to cordtex10 at a spacing of
0.8m centre to centre were charged in the
perimeter holes.
•For the perimeter holes, cordtex10 was used to
connect the de-coupled charge only. Initiation was
done using Smartdets
CHOICE OF INITIATING SYSTEM
•In order to reduce vibration , single-hole
firing was required
•Use of Smartdets was decided upon to
achieve single-hole firing and to blast
perimeter holes as pre-split together with the
‘production’ holes
•Hand lashing using buckets was employed
therefore fine fragmentation required
CHALLENGES
•Choosing a Powder factor to produce fine
fragmentation without causing damage to steel
works that kept water away
•To reduce to minimum the blast induced
vibrations so as to keep the steel works intact
•Communication difficulties with customer during
operations as only one was able to speak English.
BLAST PATTERN
DRILLED AREA READY FOR CHARGING
CHARGING IN PROGRESS
TIMING WITH SMARTDETS
BLAST AREA CHARGED
LAST PILLAR READY FOR CHARGING
FRAGMENTATION
FRAGMENTATION
FIRST PILLAR CONSTRUCTED
PILLAR CONSTRUCTED
COMPLETED PILLARS ACROSS THE RIVER
COMPLETED BRIDGE
COMPLETED BRIDGE
CUSTOMER SIGN - OFF
WITH CUSTOMER
Thank You
Thank you