Construction of a new tunnel to link two major highways in Auckland, New Zealand has reached a major milestone with relaunch of the tunnel boring machine (TBM) to construct the second bore.
Main contracting joint venture of Fletcher Construction, McConnell Dowell and Obayashi has already completed one 2.4km tunnel drive on the Waterview Connection using one of the largest Herrenknecht earth pressure balance TBMs in the world.
The Waterview Connection is currently New Zealand’s largest construction project and will close a gap in Auckland’s existing Western Ring Road.
The TBM – named Alice - completed the first drive in at the end of September - 11 months after it was launched and achieving rates of up to 126m per week. Since the breakthrough work has been underway to reposition the 14.46m diameter TBM to construct the second bore.
The TBM has been designed with relatively large openings in the shield for optimum removal of the excavated material and was specifically designed for the expected geology of sandstone and siltstone. The TBM has been designed to allow the cutting tools to be changed from the rear area and ripper tools for softer grounds were are replaced with disc cutters for harder rock when needed.
Tunnelling work is expected to be completed next year and the tunnel is scheduled to be opened to traffic at the start of 2017.