After the Kaikoura earthquake in November 2016, the steep coastal slopes north and south of the town were severely affected by rockfall, landslide, and debris flow issues. The immediate response included heli-sluicing and scaling, while the long-term solutions included permanent slope remediation designs to mitigate against future failures.
This site was approximately 130m long, and NCTIR engineers identified a potential shallow failure zone extending some 30m upslope above the rail. With KiwiRail’s main south trunk line running along the base of the slope, a permanent solution was required.
GeoStabilization was awarded the project through a competitive tender process based on our experience constructing these systems and our professional approach to construction methodology.
The design consisted of a 130m long 3.5m high Geobrugg SL-150 shallow landslide barrier. The system required both lateral and upslope anchors to support the structure, as well as robust reinforced concrete foundations for the posts. A total of 19 posts were needed to support the SPIDER® mesh panels. The barrier was located on soft, recent landslide debris, which made drilling difficult as the ground was subject to collapse. We proposed utilising self-drilling grout flush anchors and our proprietary T40 low-carbon steel hollow bar for all the anchors. NCTIR understood the benefits of this low-carbon bar and specified it on many sites throughout Kaikoura.
The proximity of the rail line provided significant working constraints but GeoStabilization’s proposed construction methodology, using our high capacity SuperNailer drill to minimise drilling time, meant the disruptions to rail operations and our construction were reduced.
This primary route across the island is built along the ridge tops where the ground is predominantly firmer, more stable, and less susceptible to flooding.