Tunnel 21 between Kaikoura and Blenheim

Tunnel 21, which is located between Kaikoura and Blenheim on KiwiRail’s Main North Line, had to be upgraded to achieve minimum clearance standards, improve line speed and importantly, increase the overall network resilience of the line following the North Canterbury Transport Infrastructure Recovery (NCTIR) project. 

Vitruvius was brought into the project based on our expertise in spatial survey and design, road design, rail geometric design and digital engineering. We surveyed the track alignment and inside of the tunnel using laser scanning technology to produce a 3D model for the track design. Using KiwiRail rolling stock data, a full spatial assessment of the tunnel was completed based on the types of rail vehicles in use on the main north line. 

Following that survey work, a thorough optioneering exercise was undertaken in partnership with KiwiRail and other specialist consultants, to explore how we would make the tunnel more resilient and improve the line speed with an efficient and effective solution. The preferred solution, which has now been delivered, involved a new offline rail alignment through a 500,000m³ cutting, and a new road over rail crossing structure. The state highway also required an online re-alignment to accommodate the works. 

This project was complex due to a number of factors: the state highway crosses over the railway lines; geometry; safety and cost for scale of earth and structural works; environmental considerations of sensitive wetlands; and private access routes.

We managed the digital model and interface to provide information from the contractor through BIM delivery.