HUNDALEE PASS RETAINING WALL

Rock Control were engaged by the North Canterbury Transport Infrastructure Recovery alliance (NCTIR) to construct a large anchored gabion basket wall, which was part of the works completed to repair damage caused by Cyclone Gita.

The failed wall had to be removed in 1.5m drops, with temporary anchors and shotcrete installed at each step. This process was repeated until an excavated level of 4.5m was reached. The slope below the excavated bench required permanent stabilisation, which was achieved by building an apron of anchored shotcrete. This apron extended onto the cut bench and formed a footing for the gabion basket wall. The gabion baskets were installed one layer at a time, with each basket requiring a 9m long anchor to be drilled through it.

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This project took place on State Highway 1, in the Hundalee Pass. Due to the location of the site, and it’s potential impact on a major arterial route, full road closure was not an option. In order to keep the road open and traffic moving, the crew excavated close to the centre line of SH1 while keeping one lane active. A staged excavation with anchored shotcrete temporary works was the only way to complete the repairs while keeping traffic flowing.