New Zealand
Background
The SH16 Lincoln to Westgate Project is being undertaken by the New Zealand Transport Agency (NZTA) to improve the North-Western Motorway for expected population growth, between Lincoln Road and Westgate.
As part of the project the North-Western Cycleway is being extended alongside State Highway 16 to create a 3 metre wide shared walking and cycling path from Lincoln Road to Westgate footbridge.
The project was undertaken by the Principal Contractor Hawkins with the retaining wall works undertaken by CLL Services and Solutions.
Scope
CMW worked closely with the contractors during the contract tender phase to develop innovative, cost effective alternative designs for a number of the walls, providing significant cost saving opportunities to the project.
Since project award we have completed additional investigations, detailed design and construction QA services for numerous retaining walls.
Findings/Challenges
The intent of the alternative designs was to provide substantial efficiencies in terms of the pile wall configurations, pile section sizes, pile spacings partitioned retaining wall height, lagging types and constructability in order to reduce the piling activities and material qualities.
In close co-operation with the contractor a mix of steel UC cantilever walls, timber pole retaining walls, gravity block walls and barrier walls were selected as appropriate solutions.
Additional geotechnical investigation works were undertaken where needed to clarify and optimise ground and groundwater models.
Design methods were carefully selected to avoid over-conservatism in the designs. Based on the encountered ground conditions specific design was undertaken and pile resistance verified for the two critical load cases 1A and 3A of NZTA Bridge Manual.
The construction works were closely monitored to ensure the encountered ground conditions aligned with the design assumptions.