Berth 3, an extension to Northport Ltd’s Marsden Point wharf facility, comprises a twin sheet pile wall to provide support to the new wharf deck and retain the adjacent reclamation. The wall type was selected to enable construction to proceed by walking a crane over the constructed wall, negating the need to use a large floating or jack up barge. The wall structure comprises twin king piles and intermediate sheet piles, 12.5m apart tied with steel bars at two levels and reinforced concrete deck top.
Design was undertaken using finite difference software FLAC to predict displacement, movement, shear and anchor loads during various stages of construction. Deflection monitoring of the wharf performance was undertaken with survey and inclinometers. This paper describes the FLAC modelling for design of the twin wall and compares monitoring results from the performance of the wall both during construction and one year following completion with predicted displacements.