SPECIALISED BLASTING By Mutale Chipoma- Explosives Engineer

WealthUnearthed

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 youThank You