Selection of Alignment and Tunnelling Methods in Urban Settings
Synopsis:
One of the challenges of the 21st century in urban settings is to provide solutions to increasing traffic. The Capitol Region around Washington D.C., USA and the Dulles Corridor Metrorail Project (DCMP), an extension to Dulles Airport (IAD), Virginia is representative of this task. Due to the congestion at the surface, the use of underground space is very often the only means of building new arteries through urban areas. This paper discusses the selection of alignment and tunneling methods in urban settings using the example of the Tysons Corner Tunnel, one keystone of the DCMP. A wide range of alignments and tunnel options was considered for the Tysons Corner segment that involves about 6 km of track and four stations. After consideration of many options that involved deep EPBM single track tunnels, shallow NATM tunnels, and a double track large bore tunnel with stations concept for the entire Tysons Corner alignment, the design now being implemented in the construction involves two 520 m long soft ground NATM tunnels with adjoining cut-and-cover sections. This paper discusses the process that led to the selection of the short NATM tunnels as the most feasible of the options considered for Tysons Corner.
Selection of Alignment and Tunnelling Methods in Urban Settings
2008 World Tunnel Congress and 34th ITA General Assembly Proceedings
September 19-25, 2008
Agra, India