City Rail Link – C3

New Zealand’s largest geotechnical and survey monitoring network mitigating construction and environmental risks across CRL’s twin tunnels and two stations.

The City Rail Link – C3 Project

The City Rail Link (CRL) in New Zealand, delivered by the Link Alliance, is the country’s largest transport infrastructure project. It involves twin 3.4km tunnels located up to 42m beneath the city streets, connecting Britomart and the city centre with the existing western line near Mt Eden. The CRL Contract 3 Project, the largest among all CRL contract packages, encompasses the construction of twin rail tunnels, two underground stations, and the redevelopment of Mt Eden Station.

Challenges & Solutions

One environmental monitoring challenge involved monitoring construction noise in Auckland’s bustling CBD, particularly at Karanga-a-Hape Station, where non-construction related noise exceedances were frequent. To tackle this issue, Sixense implemented Nora, an advanced artificial intelligence system that accurately distinguishes between on-site and ambient noise, effectively resolving the monitoring challenge. Challenges in monitoring tunnel canopy tubes were overcome by installing inclinometer casing with horizontal In Place Inclinometers (IPIs), ensuring precise monitoring. Another challenge, monitoring the NAL (North Auckland Line) rail track & data analysis, involved implementing a survey network with real-time 3D monitoring, enabling calculation of deformation parameters such as twist, cant, and gradient of the tracks.

What We’ve Delivered

In terms of monitoring, the CRL C3 project features the largest geotechnical and survey instrumentation installation on a single project in New Zealand to date. The monitoring network comprises more than 3,500 prisms monitored by 44 automatic total stations, 76 in-place inclinometers, numerous piezometers, and various other essential geotechnical instrumentation. This comprehensive setup plays a crucial role in ensuring the successful construction of the City Rail Link’s stations and tunnels. By seamlessly integrating data from a variety of monitoring instruments into Geoscope, Sixense efficiently mitigates risks in major infrastructure projects, consolidating real-time monitoring capabilities within a single platform.