Auckland City Rail Link, Contract C2: Comprehensive monitoring of the construction site and surrounding

The City Rail Link (CRL) is using twin 3.4 kilometer long tunnels, up to 42 meters below the city streets, to create an underground rail line linking Britomart and the city center 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 construction of this tunnel underneath Auckland’s city center is a major challenge requiring a robust and innovative approach to construction monitoring.

Next to Queen, Albert and Victoria Streets in Auckland have 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 meter deep trench was going to be dug close to your foundations, you’d most probably want reassurance that systems were in place to protect your asset. SIXENSE has been appointed to provide assurance for Albert Street’s property owners, insurers, Auckland Transport and the Connectus project team, a joint venture partnership between Hawkins Infrastructure and McConnell Dowell. Connectus is delivering Contract 2 which is one of CRL’s first two contracts and involves the construction of 350 meters of twin cut and cover tunnels along Albert Street, between Custom Street and Wyndham Street. It also involves diverting an existing storm water tunnel that runs under Albert Street. The monitoring network mainly consists of 9 Cyclops performing 24/7 prism and reflectorless monitoring with millimetric accuracy.

Other instrumentation solutions have also been deployed including inclinometers and piezometers. Each shaft has these, monitoring the movement of the retaining walls during excavation. Once excavation of the cut and cover begins, additional piezometers and inclinometers will be installed around the perimeter and strain gauges will be installed on struts within the excavation. Real-time monitoring and alarm management system are in place, managed by a permanent team of SIXENSE engineers and technicians, plus remote assistance.

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