Ground Engineering
Te Henga Road — Landslide Repair
550mm diameter bored piles with concrete encased steel 250UCs and a Geosynthetic Confined Soil retaining wall — permanent repair of a flood-triggered underslip on a critical West Auckland road.
- Location
- Te Henga Road, West Auckland
- Client
- Fulton Hogan
- Designer
- Mott MacDonald
- Timeline
- Construction August — November 2024
- Scope
- Concrete bored piles, GCS retaining wall, drainage
Design
Investigating the Cause, Engineering the Fix
Significant flooding in West Auckland caused an underslip failure on Te Henga Road, leading to the closure of the eastbound lane. Historical documentation indicated slope instability spanning approximately two decades at this location. GSI was engaged by Fulton Hogan to investigate the failure and design a permanent repair.
GSI's design addressed multiple constraints: maintaining access for residents and school buses, ongoing slope instability, high groundwater, and a nearby stream requiring environmental controls. The solution combined 27No. steel-reinforced concrete bored piles at 5.4 m depth for structural ground stabilisation with a Geosynthetic Confined Soil (GCS) retaining wall to restore full road dimensions, plus an integrated stormwater and drainage system to address the factors that caused the initial failure.
Build
27 Concrete Bored Piles and a GCS Retaining Wall
The remediation was delivered in phases: earthwork removal of slip material, installation of temporary sheet piling to manage the active slip and poor ground conditions, and then drilling and concreting of 27 steel-reinforced bored piles at 5.4 m depth to provide permanent structural support.
The GCS retaining wall was then constructed using Cirtix's Staragrid and Duramesh panels, along with compacted GAP65, restoring full road dimensions and carriageway width. Works were carried out within the constrained road corridor throughout the winter wet season, with traffic management maintained and active slip conditions managed to protect crews. An integrated stormwater and drainage system was installed to manage the groundwater and surface water conditions that triggered the failure.
Deliver
Te Henga Road Restored, November 2024
The GCS wall restored full road dimensions while the bored piles ensured long-term structural stability. The integrated stormwater and drainage system addresses the factors that caused the initial failure, providing resilience against future rainfall events — not just a structural fix, but a permanent solution to the underlying cause.
Te Henga Road was restored to full access by November 2024, within programme and to Auckland Transport's satisfaction. The project demonstrates GSI's ability to investigate, design, and build a complex ground engineering solution under one contract — delivering faster results than the traditional multi-firm approach in a time-sensitive post-flood repair. The Te Henga slip repair is a model for how permanent, cause-addressing solutions can be delivered efficiently under a single design-build contract.
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Related
Problem
Slope Instability →Related Projects
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Problem?
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