I-90/I-93 Interchange
Location: Boston, Mass.
Interbeton, Inc. as part of a joint venture, is constructing this $397 million project located at the intersection of I-93 and the eastern terminus of the Massachusetts Turnpike (I-90). It is the largest construction contract ever awarded by the Massachusetts Turnpike Authority. The joint venture is using jacked-boxed tunnels under the active Amtrak rail lines at South Station; this method is the only means to construct tunnels under the tracks without interrupting rail service. Project is scheduled for completion in January 2003.
Project Features:
- 10,000 feet of precast, post-tensioned viaduct
- 3 jack-boxing tunnels with similar cross sections - 80 feet wide by 40 feet high by 160, 250 and 370 linear feet
- 3,000 feet of cut-and-cover tunnel
- 3,700 feet of cast-in-place boat section
- 5,600 feet of surface roads with the associated utility work and a pumping station
- 150,000 cubic yards of soil mixing and fill in the Fort Point Channel
Unique Construction Methods:
- This is the world's largest jack-boxing project, with the first two boxes successfully pushed into place in August 2000.
- To stabilize the soil and provide earth support systems, the contractor constructed slurry walls, installed drilled shafts and used various soil stabilization techniques that included ground freezing, jet grouting and shallow soil mixing.
- Freezing the soil mass, a 3 to 4 month endeavor, involves installing pipes into the soil and circulating brine; over 1,200 pipes are being used to freeze the soil on the project.
- As trains move overhead, the tunnel sections move through the ground about 20 feet below the tracks at a rate of between 3 and 6 feet per day.
Awards:
- National Value Engineering Award for best technical value engineering change proposal to Big Dig Contracts
- Grand Award Winner ACEC's 2000 Engineering Excellence Award
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