The rock slope at site SR30 on State Highway 1 south of Kaikoura was significantly affected by landslide instability during the November 2016 Kaikoura Earthquake. Before the rail and road corridor to re-open, rockfall source treatment was required. This took the form of anchored steel mesh secured with soil nails, and had to be done first to allow access to the lower reaches of the slope for further remedial work.
Abseil Access was contracted to install over 550 hollow-bar anchors, up to 6m deep through layers of varying ground conditions. The work was carried out with a ‘top-down’ methodology due to the potential risk of rockfall. Three suspended A-frame top-hammer, self-drilling rigs were used to install the soil nails. The first phase of the works involved scaling & blasting, and vegetation removal. All site works were coordinated with KiwiRail approved RPO’s and a traffic management team for road control.
The slope itself presented significant problems regarding access, with all deliveries of materials needing helicopter lifts to the site. As the anchors were completed, the slope was overlaid with 8500m2 of rockfall netting. 10% of the anchors were subject to load tests, and nine grout samples per day were taken as part of the QA management plan. Each anchor was tensioned to 40Nm using a calibrated torque wrench.