High-strength woven geotextiles were installed at the subgrade interface to distribute loads and reinforce embankments constructed over weak alluvial and estuarine soils.
Ground improvement measures were sequenced along the corridor to accommodate variable ground conditions, severe weather impacts, and long-term construction phasing.
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A new four-lane expressway was developed across the Bay of Plenty as part of the Takitimu North Link between Tauranga and Ōmokoroa via Te Puna. The project addressed increasing traffic demand along the State Highway 2 corridor, where existing infrastructure no longer met required safety, resilience, and efficiency standards.
The alignment crossed low-lying alluvial and estuarine soils with highly variable strength and compressibility. These ground conditions presented a fundamental risk to embankment stability, long-term settlement, and construction sequencing. Early intervention at the subgrade level was required to manage these risks and to support durable roadway performance over the full design life.
The primary challenge involved constructing stable embankments over weak and compressible soils across a greenfields corridor. Settlement control and load distribution needed to be addressed at scale while maintaining construction progress along an extended alignment with varying ground conditions. The project also encountered external pressures, including severe weather impacts from Cyclone Gabrielle, which affected site access, logistics, and supply planning.
All materials incorporated into permanent works were required to meet certification standards. Ground improvement measures needed to accelerate consolidation, limit differential settlement, and provide reliable reinforcement under staged construction loading. Any disruption to material availability or installation sequencing carried the risk of delaying the wider construction program.
The ground improvement strategy combined high-strength woven geotextiles, geogrid reinforcement, prefabricated vertical drains, and separation and drainage layers to stabilize embankments and manage settlement across the alignment. The design incorporated MIRAFI® PET Series geotextiles, including MIRAFI PET1200/50, MIRAFI PET1000/50, and MIRAFI PET800/50 high-strength woven geotextiles to provide tensile reinforcement and distribute loads over weak subgrades. MIRAGRID® GX biaxial geogrids, including MIRAGRID GX200/50, MIRAGRID GX130/30, MIRAGRID GX100/30, and MIRAGRID GX40/40, were used to enhance embankment stability and performance under traffic loading.
Settlement acceleration was achieved through the installation of Alidrain AD230 prefabricated vertical drains, deployed at scale to reduce consolidation timeframes and support staged embankment construction. MIRAFI RSi and MIRAFI H2Rx geotextiles were used where separation, filtration, and moisture management were required within the pavement and earthworks structure.
In total, the project utilized more than 300,000 m² of high-strength woven geotextiles, over 190,000 m² of geogrids, and more than 645,000 m of prefabricated vertical drains.
By integrating reinforcement and drainage into a coordinated ground improvement system, the design mitigated the key geotechnical risks along the corridor. The approach improved embankment stability, controlled settlement, and enabled efficient construction sequencing across challenging terrain. Completed sections of the expressway delivered safer and more resilient transport links for the Ōmokoroa, Tauranga, and wider Bay of Plenty communities, while establishing a robust foundation for the remainder of the project.