ABSTRACT
The method of construction offers a viable solution for tunneling in soft marine ground conditions, in highly active seismic regions, in both inland and offshore environments, in constrained urban sites, and where there are environmentally sensitive conditions. In many circumstances, the immersed tunnel will be a cost-effective solution that is competitive with bridge and bored tunnel crossings of waterways. There are some obstacles to overcome with regard to perception, for example, the immersed tunnel often gets some unfair press when it comes to environmental impact. The process of education in this respect will take some time and will always be necessary because of the infrequent occurrence of immersed tunnel projects. However, projects such as the Fehmarnbelt crossing between Denmark and Germany, where a fair and full evaluation between bridge and tunnel, taking into account temporary and whole life impacts, has been carried out and shown the tunnel to be favorable, will help the industry’s understanding enormously. Hopefully projects such as this, together with this book and the ongoing work of the International Tunnelling Association (ITA), will help prospective project sponsors understand immersed tunnels better. To illustrate the current extent of immersed tunnel development, some notable achievements are given in Table 18.1.
