Investigation, Design & Construction of a Composite Road Embankment Raroa Road, Wellington

Cracking and subsidence was observed in the Raroa Road carriageway following a period of heavy rain. The site is located 500m from the main Wellington Fault. The topography of the site is steep. Remedial works have been designed and constructed to reinstate the 200m length of road to modern stability requirements including seismic design. Remedial works include a combination of a geogrid reinforced slope, fill buttress, drainage improvements, cantilever pile and tied-back pile retaining walls.

The project encountered difficult and variable surface and sub-surface conditions and unforeseen groundwater flows during construction. Flexibility and contingency provided in the design and ongoing design involvement throughout the construction enabled the project to be completed efficiently. Modifying and fine-tuning the design throughout the project and challenging standard design and construction techniques resulted in an innovative, efficient solution.