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Rockfall protection and slope stabilisation above the twin tunnel portals south of Kaikoura 

Project Overview


SH1 and several tunnels south of Kaikoura were closed after the 2016 7.8 magnitude Kaikoura Earthquake as a result of a significant slope failure and then frequent high energy rockfalls. The slip occurred above the tunnels on the peninsula and continued up a razor back ridge for over 100m that was only several meters wide at its narrow point, with rocks and debris falling each side of the ridge.


The slope and ridge line required approximately 4000m2 of an active G65/3 TECCO mesh system anchored back to the rock and soil face to stabilize the soil profile of the failed ridge line and the rock face directly about the SH1 tunnels.


Geovert Solution


The collapse of the crest when test anchors were installed required a full review the construction approach working closely with the designers as we moved to a ‘gentler’ grout flush technique to reduce impact of air into the unconsolidated soil. To achieve this several grout stations had to be set up as drilling 80m above the road, this including pumping from the roadside to an intermediary location to then pump trough the drill heads into the ground. Geovert looked at ways of improving the construction program and introduced a crane and our high reach telehandler drill for drilling above the portals and where space allowed.

Our ability to quickly switch anchoring and grouting techniques with out delay to the project, and the introduction of higher production high reach drills in the lower areas, ensured the works were completed more efficiently than with lightweight wagon drills that were used for the higher areas. With close to 1000 No. 40/16 hollow or 32mm solid bar anchors drilled from 6-9m in depth, ensuring a significant program saving.

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