Repairing
the largest tunnel boring machine ever built poses a immense challenge
to the ingenuity and resources of engineering experts in Seattle. - See
more at:
http://sourceable.net/repairing-the-worlds-biggest-tunnel-machine/#sthash.wvUIUuJt.dpuf
Repairing the largest tunnel boring machine ever built poses a immense
challenge to the ingenuity and resources of engineering experts in
Seattle. http://sourceable.net/repairing-the-worlds-biggest-tunnel-machine/
By Marc Howe, August 8, 2014
Big Bertha is the largest tunnel boring machine ever built in terms of diameter, measuring 17.5 metres, or almost six storeys in height, from top to bottom.
The machine was designed for the
specific purpose of burrowing beneath the waterfront of Seattle as part
of the US$3.1 billion Alaskan Way Viaduct Replacement Program. The
tunnel excavated by Big Bertha would be the biggest part of the program,
enabling the replacement of an obsolete viaduct dating from the 1950s
which was found to be unstable following an earthquake in 2001.
The machine was originally scheduled to
traverse a distance of over 2.7 kilometres in a pit approximately 35
metres below the surface of the earth. Its journey came to an abrupt
halt back in December after covering only the 300 metres due to a
malfunction the cause of which is still hotly contested by the parties
to the project.
According to the tunnel’s contractor,
the boring machine struck a 20-centimetre steel pipe which caused rock
and debris to enter its seal and bearing system. State-hired
transportation experts, however, assert the pipe had no bearing
whatsoever on the mammoth machine’s break down.
The ensuing rescue operation, referred
to euphemistically by workers as “the Intervention,” will entail immense
effort and cost due to the size and complexity of the
tunnelling device, as well as its subterranean location.
Workers first have to build a shaft
to reach Big Bertha, using as much as concrete as is contained by a
medium-sized office complex. The shaft first requires the creation of a
rink of pilings, in order to prevent its collapse once excavation work
begins in earnest.
Once the shaft is complete, Big Bertha,
which still has limited functionality, will be turned around and driven
through the concrete pilings to the middle of the shaft, where it will
be suspended on a giant cradle.
The front end of the device, which
itself weighs 2,000 tons, will then be hoisted from the tunnel using a
rail-mounted crane perched precariously at the brink of the shaft.
After being lowered onto the waterfront,
workers will repair the retrieved part under the watchful eye of
managers from the Japanese company responsible for its construction, adding around 200 tons of steel to the device as a reinforcing and strengthening measure.
The front piece will then be lowered back into the underground tunnel to be reattached to the rest of the boring machine’s body.
Despite the immense rigours
of endured
thus far, putting Big Bertha back together comprises the most
challenging part of the repair process due to the sheer complexity of
the machine and the difficulties involved in achieving a
precision reintegration of the amended front piece.
Work on insertion of the piling rings
commenced toward the end of the northern hemisphere spring, while the
entire repair job expected to conclude in March of 2015, with an
estimated price tag of US$125 million.
Big
Bertha is the largest tunnel boring machine ever built in terms of
diameter, measuring 17.5 metres, or almost six storeys in height, from
top to bottom.
The machine was designed for the
specific purpose of burrowing beneath the waterfront of Seattle as part
of the US$3.1 billion Alaskan Way Viaduct Replacement Program. The
tunnel excavated by Big Bertha would be the biggest part of the program,
enabling the replacement of an obsolete viaduct dating from the 1950s
which was found to be unstable following an earthquake in 2001.
The machine was originally scheduled to
traverse a distance of over 2.7 kilometres in a pit approximately 35
metres below the surface of the earth. Its journey came to an abrupt
halt back in December after covering only the 300 metres due to a
malfunction the cause of which is still hotly contested by the parties
to the project.
According to the tunnel’s contractor,
the boring machine struck a 20-centimetre steel pipe which caused rock
and debris to enter its seal and bearing system. State-hired
transportation experts, however, assert the pipe had no bearing
whatsoever on the mammoth machine’s break down.
The ensuing rescue operation, referred
to euphemistically by workers as “the Intervention,” will entail immense
effort and cost due to the size and complexity of the
tunnelling device, as well as its subterranean location.
Workers first have to build a shaft
to reach Big Bertha, using as much as concrete as is contained by a
medium-sized office complex. The shaft first requires the creation of a
rink of pilings, in order to prevent its collapse once excavation work
begins in earnest.
Once the shaft is complete, Big Bertha,
which still has limited functionality, will be turned around and driven
through the concrete pilings to the middle of the shaft, where it will
be suspended on a giant cradle.
The front end of the device, which
itself weighs 2,000 tons, will then be hoisted from the tunnel using a
rail-mounted crane perched precariously at the brink of the shaft.
After being lowered onto the waterfront,
workers will repair the retrieved part under the watchful eye of
managers from the Japanese company responsible for its construction, adding around 200 tons of steel to the device as a reinforcing and strengthening measure.
The front piece will then be lowered back into the underground tunnel to be reattached to the rest of the boring machine’s body.
Despite the immense rigours of endured
thus far, putting Big Bertha back together comprises the most
challenging part of the repair process due to the sheer complexity of
the machine and the difficulties involved in achieving a
precision reintegration of the amended front piece.
Work on insertion of the piling rings
commenced toward the end of the northern hemisphere spring, while the
entire repair job expected to conclude in March of 2015, with an
estimated price tag of US$125 million.
- See more at: http://sourceable.net/repairing-the-worlds-biggest-tunnel-machine/#sthash.wvUIUuJt.dpuf