Civil Engineering Reference
In-Depth Information
Settlements of the motorway were carefully measured using instruments
located on 9 m high towers monitoring the carriageway on a 5 m grid and
giving displacements in three-dimensional coordinates in real time, as shown
in Figure 5.75. With careful jacking and excavation the maximum recorded
settlement was 26 mm.
5.10.3.2 I-90 Highway Extension, Boston, Massachusetts, USA
The massive Central Artery highway reconstruction in Boston (the so called
'Big Dig' project) involved major improvements to the road infrastructure
and in particular the I-90 highway. As part of this project the I-90 had to
pass beneath eleven active railroad tracks, which carry commuter and
mainline trains into Boston's busiest rail terminal, South Station. The
railroad operation had to remain in service throughout the construction
project. In order to achieve this, tunnels were jacked underneath these
railroad tracks. The jacked tunnels formed a link between the immersed
tube tunnel under the Fort Point Channel and the cut-and-cover sections
(Figure 5.77). The cover depth between the top of the tunnel sections and
the railroad tracks was approximately 6.1 m (20 ft).
The I-90 Highway Extension in Boston was constructed by the Slattery,
Interbeton, J.F. White, Perini Joint Venture with the jacked box tunnelling
design, planning and installation services provided by Edmund Nuttall
Limited in association with John Ropkins Limited. The jacked box tunnels
were constructed in 2001.
Fort Point Channel
(location of the
immersed tube
tunnel)
Railroad lines
Jacked box
starting pits
during
construction
Figure 5.77
An overview of the jacked box sites in Boston showing the
railroad lines and Fort Point Channel (courtesy of
Massachusetts Turnpike Authority)
