Title:
Designing for a 100 Year Life in a High Chloride and Acid-sulfate Environment
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Publication:
CIA
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Issue:
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DOI:
Date:
2/14/2011
Abstract:
Ballina Bypass is an 11.4 km long section of the Pacific Highway Upgrade. The Bypass runs from the intersection of the Bruxner and Pacific Highways south of the town of Ballina to the intersection of Ross Lane and the Pacific Highway, north of the town near Tintenbar. Designing structures for durability was a key component of the design process. Numerous bridges, drainage and other civil structures have been designed to achieve a design life of 100 years in aggressive ground conditions.
Site investigations found widespread acid-sulfate soils, particularly at low lying floodplain areas. The route alignment is near a tidal creek in many places. Many drainage structures will act as irrigation channels, and will be partially submerged, permanently. Thus borehole analyses were carried out at various locations along the route to measure the sulfate content, chloride content and the acidity of the soil. Resistivity and redox potentials further confirmed aggressive soil and groundwater.