A successful trial of vacuum consolidation at the Port of Brisbane

Menard - Permeable Reactive Barrier
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The Port of Brisbane is located at the mouth of the Brisbane River in South-East Queensland, Australia. In recent years, the modern purpose built Fisherman Island’s Port, has seen rapid development due to increased trade growth. The expansion and development of future Port land is critical to ensure that the Port’s facilities can expand at a rate to meet this growth.

Reclamation is in progress, over the 235 hectares of sub-tidal lands contained within the perimeter Seawall, built in 2005 for the Future Port Expansion (FPE). In late 2005, the Port of Brisbane Corporation (PBC) engaged Coffey Geotechnics (Coffey) as its geotechnical advisor for development of the FPE reclamation areas.

The subsurface conditions in the recent reclamation and FPE areas are significantly different from the previously developed areas at Fisherman Islands. The in-situ compressible clay is much deeper, up to 30m thickness. The reclamation is carried out using channel maintenance and berth dredging materials resulting in 7~9m metres of mud being deposited on the original seabed and being capped off with sand.

Generally, consolidation timings for these undeveloped areas were predicted to be well in excess of 50 years if surcharging was the only treatment employed, as has been past practice at the Port. Settlements in the range of 2m to 3m were also forecasted.

Given the pressures of creating additional usable Port land in time frames approximately half of those achieved in the past, it was decided that new techniques to speed up the consolidation process needed to be employed to meet the land development timings.

To identify suitable ground improvement techniques to suit local conditions, PBC in 2006 selected Austress-Menard (Menard) to conduct a design and construct trial using vacuum consolidation on a 15,000m2 area along the site boundary of the existing reclamation area where any instability will significantly impact the adjacent Moreton Bay Marine Park and purpose built Migratory Wader Bird Roost (Boyle et al 2007).

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