Last November, a 7.8-magnitude earthquake caused more than 100,000 cubic meters of rock and debris to tumble down and bury the road below Ohau Point in the South Island of New Zealand. The Rock Remediation Technicians (RRTs) of Hiway GeoStabilization (HGS) have been tasked to mitigate future hazards and secure the remaining rock face with rock anchors, ring net drapes, and Geobrugg’s high-tensile steel TECCO mesh. Click here to read more.
HGS is a joint venture between GeoStabilization International of the USA and the Hiway Group in New Zealand. Soon after its formation, HGS was contracted by the North Canterbury Transport Infrastructure Recovery (NCTIR – the alliance formed to repair the road and rail networks between Picton and Christchurch following the November 2016 Kaikoura earthquake) to help rebuild the infrastructure North of Kaikoura. NCTIR aims to have the road open by this coming Christmas, but work will work continue into 2018 to complete a number of safety and resiliency improvements along the main highway in the area.
As shown in the video contained in this link, the experienced RRTs wear full-body harnesses and utilize secured lines to ensure their safety as they descend the steep, near vertical rock slope to secure the ring net and mesh drape to the face. HGS’ efforts, led by Mat Avery & Jonty Pretorius, began in March of this year and they have just completed installation of the largest rockfall drape ever to be installed in New Zealand.
Following the installation of the ring net and mesh drape, which covers the top 5,800 m2 of the rock face, the crew will work to remove all of the loose rocks from the base of the drape down to the road level, an approximately 12,500m2 area. Once the rocks are removed, construction access can increase below the rock face allowing roading crews to continue construction of the new road. The HGS crew will then move back to the top of the bluff to install 611 rock bolts through the drape in a 3-meter grid pattern. This will secure the ring net and mesh to the face, while also anchoring the larger loose rocks, and completing the permanent design of the remediation allowing safe public access to the new road below.
While the views of the ocean and wildlife are breathtaking, these crews have battled unforgiving weather throughout the project. The work performed by HGS is crucial for the safety of the traveling public who will be able to once again travel past Ohau Point after the road has been repaired.
A variation of karst sinkhole grouting is the grouting of mined coal seams and workings located below existing infrastructure that exhibit the potential to propagate to the surface and cause sinkholes and/or subsidence.