ICB was engaged to stabilise a failing slope threatening a key transport route in Puhoi. Using a deep-piled palisade retaining wall with tieback anchors, ICB delivered a high-resilience solution while keeping traffic moving throughout construction.
Quick Facts
46 concrete piles (Ø750mm) were driller 15 metres deep to stabilise the slope
24-metre-long anchors were used to support the retaining wall
New drainage and stormwater system was installed to prevent future slips
One lane stayed open during the entire construction to keep traffic moving
LOCATION
Ahuroa Road, Puhoi, Auckland
CUSTOMER
Auckland Transport
SERVICES
• Slope remediation
• Palisade retaining with tieback anchors
• Deep piling
The Challenge
A major slip on the southern side of Ahuroa Road compromised the westbound lane and nearby stormwater infrastructure. With ongoing movement and a risk of complete road failure, the project required urgent remediation in geotechnically sensitive ground. Maintaining traffic flow and avoiding a full road closure were top priorities, further complicated by poor weather and restricted site access.
The Solution
ICB delivered a deep foundation solution using a tieback palisade retaining wall system. The method involved:
Excavating to 4m below road level to bench the slope
Installing 750mm diameter reinforced concrete piles at 1.5m spacing, drilled 15m deep
Placing 24m tieback anchors to offload lateral pressure from the piles
Constructing access ramps with compacted geogrid-reinforced hardfill
Pouring a reinforced concrete capping beam to unify the pile heads and house anchor ducts
Backfilling the wall with 300mm of drainage aggregate and installing timber rails
Despite persistent rain and soft ground, ICB maintained one-lane traffic flow throughout, ensuring public safety and continuous access for the surrounding community.
The Impact & Results
The completed structure restored the road’s integrity, safeguarded critical infrastructure, and delivered long-term protection against future slips. With zero safety incidents and minimal commuter disruption, the project showcased ICB’s ability to manage urgent, high-stakes stabilisation under live road conditions.
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