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Geotechnical advice, Darwin East Arm Wharf, Northern Territory, Australia

THE PROJECT

Opened in 2000, the East Arm Wharf is a 750 m long facility located in Darwin Port. The largest facility on Australia’s north coast, the facility is capable of accepting vessels up to 80,000 tonnes, with a maximum draft of 15 m. The Wharf comprises a bulk liquid berth, a common user facility, a container facility and a bulk loading berth. The container berth is served by a rail-mounted container crane with a heavy lifting capacity of 70 tonnes at 10 m outreach.

PSM was engaged to provide specialist advice on several complex geotechnical issues associated with wharf construction.

engineering and technical opportunities

A huge tidal range of 7.8 m has resulted in a very high wharf face. Construction of the wharf structure on existing bund built from materials under water, makes it susceptible to deformation.

Other engineering and technical opportunities included:

  • A range of in-situ material requiring detailed investigation and analyses
  • Fill materials to backfill the wharf being limited to weathered rock requiring particular attention
  • Assessment of the phyllite bedrock critical to the capacity of the structure.

approach AND innovation

PSM’s tailored approach included:

  • Assessment of the lateral load capacity of the weathered phyllite bedrock into which the sheet piles were driven
  • Assessment of deformation of the wharf structure and the effects on tension anchors
  • Monitoring of completed wharf
  • Provision of advice for Stage 2 regarding construction methodology for the backfilled wharf
  • Development of a comprehensive geological and geotechnical model
  • Analysis of interaction with sheet piles to assess risk to design from various potential failure mechanisms
  • Inclusion in the design of structural pins at the base of sheet piles to improve strength
  • Regular monitoring reviews to ensure appropriate performance.

OUTCOMES

PSM’s involvement enabled resolution of key technical challenges and completion of structure without incident. As a result of ongoing monitoring the client is able to manage risks relating to time-dependent deformation of the geotechnical materials used in the wharf’s construction.

Services: #Geological #Geotechnical #Phyllite bedrock

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