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Blasting at the Southern Expressway Duplication

Blasting work on the project commenced in July 2012 and, due to the proximity of dwellings and various critical infrastructure assets, proven expertise was essential to ensure the project goals of achieving minimal disruption to the local community were met.
 
Impact Drill & Blast has made available two Sandvik Pantera 1100 hydraulic rock drills for the project and has engaged local company TecBlast Services to provide support and additional expertise in blasting and explosives delivery and storage.
All blasting is done during the daily closure of the existing expressway at about 12.30pm, which means explosives deliveries, loading, stemming, tie-in and firing of each shot must be completed during the morning of the blast.
The tight schedule requires detailed planning to ensure the benches are adequately prepared, marked out for drilling and drilled prior to the designated day of the blast, and also to meet the needs of the explosives supplier for forward ordering of blasting explosives and initiators. 
Impact?s general manager Rodney Krins has been pleased with the progress so far.
?Impact has had to organise drills and personnel to meet the demands of the project and considering the linear nature of the excavation, where rock removal can only be done from one end, we believe we have successfully optimised our performance,? Krins said.
Blasting on the project requires a minimum of forward rock movement towards the existing roadway and a methodology that eliminates flyrock. 
{{image2-a:R-w:200}}Impact?s senior shotfirer David Hamilton pointed out the importance of precision in achieving this. ?We endeavour to prepare the initial drilling area and mark out for drilling within tight tolerances,? he explained.
?The holes are surveyed and the plan is reviewed for hole depths and burdens to ensure our goal for minimal vibration is achieved.
?We laser profile as required to ensure accuracy in individual hole burdens and blast monitor at multiple locations. We deploy Australian-made Texcel seismographs to record vibration and air blast from the blast. All this has delivered good results. Loading and tie-in is carefully scrutinised to ensure we have complete and accurate results.? 
The majority of the rock is on the Darlington escarpment between Seacombe Road and Majors Road and is a hard blue dolomite with some clay intrusions. It provides high quality rock fill for the project as well as on-site crusher feed. 
Impact?s partnership with TecBlast has been built over the past five years and they combine to provide drill and blast services to mines and quarries in South Australia. Murray Gannon, the proprietor of TecBlast, described the benefits.
?Our work here with Impact allows us to combine our expertise, equipment, vehicles, magazines, personnel and explosives licences and we both benefit,? Gannon said. ?We extend this service to all parts of SA, with this project being by far the highest profile job that we?ve combined for so far.? ?
Sources: Impact Drill & Blast, TecBlast

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