TUNNEL 21

Rock Control were engaged to provide specialist anchoring and shotcrete works for the new Main North Line rail construction and realignment to pass under State Highway 1. The site itself is remote and exposed resulting in construction challenges and less than desirable conditions.

 

The work was broken into two main stages, shotcrete within the underpass and anchored shotcrete north of the portal opening. The underpass works required multiple visits and sprays to stabilise the cut material between secant piles, as well as a 600mm thick lower reinforced impact wall the full length of the underpass. The impact wall had a screeded finish followed by a fine overspray to form a planar finish down the length of the tunnel. The northern portal wall required staged anchoring and shotcrete works to enable the excavation contractor to complete the required cuts to depth.

 

Specialist double corrosion protection anchors and headworks were supplied and installed by Rock Control with 100% production testing performed across the anchors. Strict quality assurance and testing was required for these works to adhere to the KiwiRail and NZTA criteria.