Drill and blast work on Southern Expressway

With over one million tonnes of hard rock to be removed, the Baulderstone Abigroup JV?s Southern Expressway duplication project in Adelaide has awarded a major contract to Impact Drill and Blast.

Blasting work on the project commenced in July 2012 and due to the proximity of dwellings and critical infrastructure assets, the expertise was essential to ensure that project goals of achieving minimal disruption to the local community were met.

Impact Drill and Blast has two Sandvik Pantera 1100 hydraulic rock drills on the project and has engaged local company TecBlast Services to provide support and additional expertise in blasting and explosives delivery, storage and personnel.

All blasting is done during the daily closure of the existing expressway at approximately 12.30pm, which means that explosives deliveries, loading, stemming, tie-in and firing must be completed during the morning of the blast.

The tight schedule requires detailed planning to ensure that benches are 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.

Rodney Krins, Impact?s general manager for South Australia and Victoria, 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,? he said.

Blasting on the project requires a minimum of forward rock movement towards the roadway and a methodology that eliminates flyrock. 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. The holes are surveyed and the plan is reviewed for hole depths to ensure our goals for minimal vibration is achieved,? he said.

?We laser profile each face to ensure accuracy in individual hole burdens and at up to seven locations we deploy Australian-made Texcel seismographs to record vibration and noise 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, jointing and weathering. It provides high quality rockfill for the project as well as an on-site crusher feed. 

Impact?s partnership with TecBlast has been built up over the last five years and they combine to provide drill and blast services to mines and quarries in South Australia.  

?Our work here with Impact allows us to combine our expertise, equipment, vehicles, magazines, personnel and explosives licences and we both benefit.  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,? said Murray Gannon, the proprietor of Tecblast.