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An Appraisal of Tunnelling in the Auckland Region for Infrastructure Development


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Author A Hodgson and J St George


Much of Auckland’s transport infrastructure has been developed on surface
with little or no consideration of underground options. Current and planned
transportation routes are now facing high costs due to land values and
increasing environmental resistance to surface development. The option of
utilising underground space becomes a feasible investment decision for these
links as well as being the only option to develop the rail network within the
inner city area. Transportation tunnels offer a quieter, more energy efficient
means of getting around with minimal impacts on the surface environment. One of
the major impediments to tunnelling is the high construction cost, which is
partly related to the risks of encountering unexpected ground conditions and/or
the possibility of causing surface ground deformations which could damage

The geology of Auckland has had substantial investigation through various
studies and projects. The sediments of the East Coast Bays Formation (ECBF)
underlie most of the Auckland urban area. It is classified as a soft rock and is
a suitable material to tunnel through using either a tunnel boring machine or a
roadheader. This paper reviews the limited amount of tunnelling completed in the
urban Auckland area, together with the international advancements that have been
made in the tunnelling industry. From the known features of the local geology
and the problems encountered historically, the likely risks of tunnelling in
Auckland are presented and ways in which those risks could be reduced and
managed, are discussed. In addition, contractual arrangements between client and
contractor are assessed with respect to complicated projects (such as
tunnelling), so that the risks can be managed to create efficient infrastructure
routes with reduced costs.