The Whitianga Waterways project involved complex engineering due to its location below sea level and the presence of marine mud under a thin layer of sand. The construction of canals and canal walls in this setting presented significant challenges.
The bridge was engineered to endure various environmental stresses, including heavy traffic, seismic activity, liquefaction, and extreme tidal conditions. The design included two tiered abutments, each 9.1 metres high, set 8 metres apart. StrataGrid™ geogrid was used to reinforce the soil mass and distribute loads, negating the need for deep drilled piles.
It used high-quality backfill within the reinforced zone and overlapped the StrataGrid™ between aggregate layers.
This method allowed for a more consistent ground settlement over time, a crucial factor in bridge construction. Integral bridge abutments with geosynthetic reinforcement, a technique not widely used in New Zealand at the time, was implemented. This approach ensures that the road and bridge settle uniformly, reducing the risk of differential settlement.
The project showcased sustainable and ecologically friendly bridge-building techniques. By using StrataGrid™ for reinforcement, the project team demonstrated the feasibility and effectiveness of alternative construction methods in New Zealand’s unique environmental conditions.
