10 | Business World Magazine |
July 2013
Weighing more than 83 tons and
reaching a height of five stories,
Bertha is indeed big, but she’s also
beautiful, especially to Washington
State Department of Transportation
workers wanting to expedite con-
struction of the new Route 99 tun-
nel. The tunnel, which will extend
beneath downtown Seattle, is part of
a $3 billion project that replaces the
aging infrastructure associated with
theAlaskanWayViaduct. Aftermore
than a year of development, the world’s largest tun-
neling machine (dubbed as “Bertha”) was recently
lowered into an 80 foot pit to begin boring through
some two miles of terra firma. Valued at more than
$80 million, Bertha was manufactured by Hitachi
Zosen in Osaka, Japan. Its drill head is more than
57 feet in diameter and equipped with more than
600 steel bits and spinning disks to effectively bore
through dirt and rock. Traditionally, these innova-
tions in excavation have to be frequently inspected
at varying stages of depth, which is problematic for
humans because in an enclosed tunnel, the pressure
at depths of only 200 feet is essentially the same as
that which exists under 165 feet of water. Replac-
ing cutting tools has generally required workers to
spend time in a hyperbaric chamber, yet with Ber-
tha, workers can make needed modifications from
inside the machine itself. Bertha is large enough to
accommodate work frombehind the drill face at at-
mospheric pressure similar to aboveground condi-
tions. An automated system basically helps retract
the cutting components into a chamber, allowing
workers to make repairs aided by hydraulic pulleys
and other mechanisms that expedite the process.
Barring any birthing pains, Bertha is anticipated to
crawl along some 30 feet per day, and the tunnel is
expected to be ready for motorists by 2015.
Birthing
Bertha
