Results
Successful removal of 25m-high, 2,000t unstable rock mass.
Road reopened safely after completion of blasting and scaling.
Protection of tunnel portal structures through controlled blasting.
Safe project delivery despite extreme alpine conditions.
Project
Solution
Joint assessment with NZTA engineers to confirm rock failure mechanism.
Installation of extensometers to monitor movement during works.
Drill and blast program with 23 holes and 300kg of explosives.
Precision blast design to maximise fragmentation and protect tunnel structures.
Post-blast scaling and inspection to stabilise the slope.
Partnership with Adventure Consultants for mountain safety and heli-lifeline access.
Project
Challenges
2,000t rock mass with less than 10% toe attachment above a state highway.
Worksite located 900m above the tunnel entrance at 1,800m ASL.
Severe alpine weather with 200 km/h winds, –18°C temperatures, heavy snow and rain.
Urgent requirement to reopen a closed national highway.
Project
Overview
Following the identification of a highly unstable 25m-high rock mass above the western portal of the Homer Tunnel, State Highway 6 was closed due to the immediate rockfall hazard. At 1,800m elevation in extreme alpine conditions, drilling, blasting, and scaling were undertaken to remove the 2,000t feature and allow the road to safely reopen.
The project involved detailed geotechnical assessment, extensometer monitoring, and precision blasting to minimise impact on tunnel infrastructure, all carried out under storm-force winds, snow events, and sub-zero temperatures with heli-lifeline access.