Boston Blockbuster
by Virginia Fairweather, Editor in Chief;Serial Information: Civil Engineering—ASCE, 1996, Vol. 66, Issue 12, Pg. 40-43
Document Type: Feature article
Abstract:
The Central Artery/Tunnel project in Boston is probably the single largest publicly-funded transportation project in the country at present. The total cost will be between $8 and $10 billion when it is completed in 2001. Part of the project at the Fort Point Channel, has been redesigned to cut a projected $500 million in construction costs. Still, the work will cost over $1.5 billion for about a mile and a half of tunnel and approaches. The area has extremely weak soils, as low as 800 psi, and temporary excavation support works for a conventional cut and cover approach proved to be too costly and impractical. This approach would also have added two years to the schedule and delayed opening the tunnel. The new design incorporates three unusual geotechnical technologies, deep soil mixing, immersed tube tunnels and tunnel jacking, to an extent never used before in this country. The urban site is extremely constricted and commuter trains, Boston's principal postal facility and a major factory have to keep operating during construction. The deep soil mixing, principally a Japanese technique, has been used here a few times, but never to the extent planned for this project. Similarly, immersed tube tunnels have also been built here, but these concrete segments are larger than any previous immersed tunnel. Tunnel jacking, primarily a European technology, has never been used in the U.S. under operating trains. Here the tunnels will be jacked only six feet beneath an operating subway tunnel. Extensive monitoring will be incorporated to limit settlement.
Subject Headings: Tunnels | Project management | Soil mixing | Jacking | Construction sites | Benefit cost ratios | Urban areas | Boston | Massachusetts | United States
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