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Concrete Cutting
& Breaking Tackles Boston's Big Dig
Boston's Central Artery / Tunnel Project - commonly known
as the Big Dig - is the largest, most complex and technologically
challenging highway project ever attempted in American history.
The project will dramatically reduce traffic and improve mobility
in this long-congested city by widening and replacing major
portions of highways and subways, most of which are being
relocated to tunnels nearly a hundred feet below ground. The
Big Dig began in 1991 and will complete sometime in 2004,
at a total cost of over $12 billion. It's a project that involves
3.8 million cubic yards of concrete, enough steel rebar to
wrap around the earth at the equator, and nearly four thousand
workers - including a team of skilled operators from Concrete
Cutting and Breaking, Inc. - Boston.
The existing Blue Line Subway Tunnel in
Boston is in the process of a complete renovation, lengthening
the platform to accommodate six instead of the four subway
cars that it now handles. The new tunnel was designed to run
north/south, perpendicular to the existing Blue Line that
runs east/west. While engineers originally planned the new
tunnel to pass above the old tunnel, it was later determined
that the new tunnel would have to be lower than expected,
placing it on an elevation that would pass through the ceiling
of the existing Blue Line. The decision was made to demolish
and remove an entire 400 foot section of the old tunnel to
accomplish this task.
After discounting implosion of the tunnel
due to the fragile foundations of the surrounding buildings,
Modern Continental, the General Contractor, contacted CCB
to cut and remove the old tunnel. To do this cuts had to be
made through the tunnel at 35' intervals so the demolition
contractor could have a clean break to finish each weekend.
The demolition work was performed exclusively on weekends
during which time the entire subway was closed down and reopened
for commuter traffic each Monday morning. Conventional demolition
was used to remove the tunnel section ends with each designated
wire saw line. This ensured that no concrete debris would
fall on the tracks below, impeding the scheduled subway service.
The wire sawing task included sawing on
one side of the tunnel at track elevation, proceeding to the
above archway, and down the opposite side of the tunnel to
end at track elevation again. CCB used core holes at each
cut location to thread the wire through and performed horizontal
wall sawing at the new platform elevation on both sides of
the tunnel in designated locations.
CCB was selected for this project by the
General Contractor for their ability to provide the timely
production schedule that was required to fulfill a tight deadline.
Other contractors such as Perini, J.F. White, etc. have also
employed CCB to perform other work on the Big Dig.
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| Over
4,000 workers per day are involved in the overall project.
When completed in 2004, thousands of cars per hour will
be routed through tunnels hundreds of feet under Boston.
|
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| The
Big Dig is the largest construction project in American
history. |
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| Underneath
Broad Street, the old subway tunnel's top is cut open. |
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| Cutting
continues on the subway line under State Street. |
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