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: Marie Le Breton
It could be a gigantic bull’s eye, or perhaps an
oil rig, as seen from a helicopter. But in fact, it is
one of the four piers of the Rion-Antirion Bridge, the
longest cable-stayed bridge in the world. Spanning the
Gulf of Corinth with its 2,252-meter suspended deck, the
structure links the Peloponnese to mainland Greece in
an unusually daring feat of engineering. The construction
environment could hardly have been more unfavorable. An
active fault-line nearby subjects the Gulf coasts to tectonic
shifts that can trigger intense seismic activity (the
Ancient Greeks believed that earthquakes were a sign of
Poseidon’s wrath, when the god of the sea would
pound his trident on the ocean floor). Add to this seismic
threat the high water depths of up to 65 meters and an
unstable sea bed, and the true measure of the challenge
immediately becomes clear. For engineers, the key was
to find a way to solidly anchor the pylons carrying the
bridge’s five spans, in such a way that they would
be able to withstand deformation without breaking in the
event of a violent earthquake. To this end, the sea bed
was stabilized by driving steel pipes into it, which were
then covered with a leveled gravel layer 3 meters thick.
The resulting base on which the pylons rest is both stable
and mobile: in the event of an earthquake, the base can
slide as much as 2 meters on the gravel beds. This innovative
seismic design ensures resistance to earthquakes rated
7 and above on the Richter scale. The bridge opened to
traffic on August 11, 2004 and is used by 10,000 vehicles
per day... whether Poseidon likes it or not. |
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