Large cross sections for soft ground and soft rock conventional tunneling projects in urban areas – recent developments in the US
With the demand for tunnels growing, especially in urban areas, the ability to construct these tunnels without disrupting congested areas on the surface has become more important. Conventional tunneling has become increasingly popular as it is very useful in these urban environments, as well as in soft ground. Conventional tunneling, also known as the New Austrian Tunnel Method (NATM) or the Sequential Excavation Method (SEM), is the construction of tunnels utilizing sequential processes and sections to excavate and support the ground. By referring to case studies, this paper discusses the importance of conventional tunneling and other state of the art ground improvement methods which have been used to great success in large cross section projects in the United States.