Geotechnical investigations associated with the Axis Fergusson Expansion

Ports of Auckland Ltd (POAL) are upgrading Axis Fergusson Terminal to increase container handling capacity in order to meet a
projected increase in trade. The upgrade includes construction of a piled wharf 320m long, mooring dolphins, 1000m length of perimeter bunds and a reclamation which will be 9.4 hectares in area and will contain 1.5 million cubic metres of fill.

The existing seabed lies between 1 m and 12 m below Chart Datum, with the surface of the reclamation at around 5.4m above chart datum, resulting in fill depths of up to 18m. The site is located in Auckland, New Zealand in the Waitemata Harbour which is drowned river valley system and which has significant depths of weak sediments. The existing terminal is constructed over the top of an old remnant ridge. The proposed reclamation is located to the east of the ridge over a valley with thick layers of weak sediments.

The main geotechnical design issues associated with this development include stability (static and seismic) of the 18m high bunds and reclamation on weak sediments, settlement of the reclamation and bunds, suitability of reclamation fill materials to obtain a reclamation of relatively low compressibility, reuse of marine dredgings, and piling options to support the wharf structure.

Geotechnical investigations have been undertaken at various stages of the project from prefeasibility to detailed design in order to obtain information about the underlying soil conditions. Investigations comprised a series of machine boreholes and Geonor in situ large vane testing undertaken from a barge in the harbour and laboratory testing.

This paper describes the geotechnical design issues associated with the development, the extensive geotechnical investigations to address these design issues, and summarises the results of these investigations.