Three Sisters may sound like the gentle name of a location, but they provided some of the most challenging drilling conditions in our company’s history, which were only overcome with patience, perseverance and the team’s dogged attitude – with the client (NZTA) happy to have the works completed successfully.
The team showed their dedication and ingenuity, battling late-winter conditions next to the Kapiti Coast on a night shift, with only a 6hr working window per shift.
The site (situated directly above SH1) although small in appearance, had numerous obstacles to overcome. The rock was a hard and unweathered Greywacke, situated on a shear-zone. Each bore had to be re-worked with the tools (DTH Hammer drill rig) until the hole was stable and clean enough to allow a CCTV survey down the length of the hole, confirming the driller’s logs and depth of the anchor to be installed.
All of the anchors tested surpassed the indicated design load of 220kN, and each anchor employed a perpendicular mortar bearing pad to spread the load and to ensure a nice snug finish on the Geobrugg G65/3 Rockfall mesh.