Monitoring of City Rail Link – C2 | New Zealand

The Project

The City Rail Link (CRL) consists of twin 3.4 km long tunnels up to 42 metres below the city streets to create an underground rail line linking Britomart and the city centre with the existing western line near Mt Eden and is key to delivering the Auckland plan, the city centre master plan, the long term plan and the integrated transport programme. The contract C2 involves the construction of 350 metres of twin cut and cover tunnels along Albert Street, between Custom Street and Wyndham Street. It also involves diverting an existing stormwater tunnel that runs under Albert Street.

Adjacent to Queen, Albert and Victoria Streets in Auckland exists some of the most valuable real estate in the country. As the owner of a multimillion-dollar building on Albert Street, knowing that a 20 metre deep trench was going to be excavated close to your foundations, you’d want assurance that systems were in place to protect your assets.

Monitoring solution

Sixense, has been engaged by Connectus (a joint venture of Hawkins Infrastructure and McConnell Dowell) and Auckland Transport to monitor the construction works, and to provide assurance for Albert Street’s property owners and insurers.

The monitoring network consisted of a network of 9 Cyclops, 12 automatic inclinometers, dozens of ground water piezometers, and hundreds of strain gauges. The Cyclops network monitored building prisms and ground surface points 24/7 with sub-millimetre accuracy. The automatic inclinometers and strain gauges monitored deflections of the retaining walls and strut compression, and the piezometers measured ground water levels around the site.

A real-time monitoring and alarm management system was put in place using Geoscope, managed by a permanant team of Sixense engineers and technicians.