A new commercial development on School Rd in Wellington required to the existing slope to be cut back to allow for a larger building footprint. Cutting back the face in the fractured Wellington greywacke required an actively stabilized system to retain the face.
Our method to utilize our custom-built high reach drill enabled our client to cut the face more quickly and in one process as we could reach all the way up with no benches required. This improved the earthworks program substantially allowing the development to progress ahead of schedule.
A flexible Geobrugg mesh with tensioned rock anchors was utilized in place of the shotcrete facing commonly used in Wellington as it allows the slope to move during seismic events, naturally drains and vegetates. Open hole drilling using a DTH was used with the drill from below only utilising rope access to install and grout the nails once the drilling was completed limiting exposure time for crew near the rotating drill. Approximately 900m2 of mesh was tensioned to the face with 200No rock anchors.
Our team on the ground were able to provide a solution for the client when a localised area within the cutting was quite badly fractured and ground collapsing during drilling. By quickly changing out the rotary drill with a backup top hammer onsite, we were able to install grout flushed hollow bar anchors that were in stocked in our yard to eliminate potential delays.