by applying a roughly 10 by 4 m concrete “patch,” notes Miller. The patch
is still there and is considered structurally sound. Unfortunately, no one knew
if there were any unexploded bombs in
the area. The existence of bombs was
a definite possibility given the tens of
thousands of bombs dropped during
the war and the fact that unexploded
ordnance dating back to the war has
been discovered and removed from
nearby sites associated with this summer’s Olympic Games.
To ensure the safety of the Connaught Tunnel project and its workers, a team of bomb disposal specialists with military experience searched
the site over a period of several months
using a heavily armored vehicle with a
magnetometer probe that was carefully
pushed down into the soil, says Miller. Working like a metal detector, the
probe revealed the location of buried
metal objects that could have been unexploded bombs. Although numerous
“anomalies” were discovered because of
the site’s heavily ferrous railroad past,
careful excavation found no ordnance,
The Connaught Tunnel includes
surface approaches on either side of the
tunnel, each about 500 m in length,
retained cuttings that lead to the tunnel portals, and the 550 m long tunnel
that extends beneath the airport apron
and dock passage.
The Connaught Tunnel was constructed as a single-bore, twin-track
tunnel at each end with twin parallel
single-track bores beneath the dock
passage, Miller says. Originally constructed as a mass concrete buttressed
cutting in the open-air portions and
as a brick-lined tunnel in the underground and underwater portions, the
twin tunnels’ structural integrity was
in danger of being compromised in the
1930s after the tunnels were scraped
several times by the keels of the larger vessels then using the docks, Miller notes. To address that problem, the
crowns of the central section of the
twin tunnels were lowered by approximately 0.9 m and reconstructed with
bolted and welded segmental linings
of cast steel, Miller explains.
The Connaught Tunnel will provide
a vital link between the sites planned for
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Walter P Moore, an engineering firm based in Houston
with more than 300 employees, has acquired
Dodson & Associates, Inc., an engineering firm
specializing in storm-water management that also
is based in Houston and has 7 employees.
SEPTEMBER 2012 Civil Engineering