The Rio-Antirrio Bridge, also known as the Charilaos Troupikos Bridge, is a two thousand eight hundred meter bridge connecting the towns of Rio and Antirrio over the Gulf of Corinth. The bridge joins two of the country’s busiest and most successful towns, making it an essential piece of infrastructure to the economy and industry of Greece.
What makes the Rio-Antirrio bridge so special, though, is that it shouldn’t even exist. According to Service Steel, almost every stage of the bridge’s construction was beset with challenges that would make any master engineer pull all their hair out.
Despite being the ideal location for a bridge, the region lies in one of the world’s most active fault lines. Due to the constant movement, the sea floor is nothing more than sand and silt, with the only solid rock suitable to build a foundation on lying sixty meters under that surface. There have been bridges built over such surfaces before, but nothing near the size of the Rio-Antirrio.
In such situations, engineers got to the solid bedrock by creating a dam around the build site, drain the water, remove the sand and silt, and then start building the foundation. This is impossible for a bridge that’s supposed to span less than three kilometres. Engineers needed to build the foundations on the sea floor as is, but that’s not the biggest problem with the sea floor though.
Seaquakes are a regular occurrence in the region, and the constant shaking makes anything sink into the ground. A sinking bridge isn’t a useful one. Engineers needed to think of a way to isolate the colossal bridge from the violent shaking, and keep it from sinking into the sand.
The solution they came up with was ingenious and frustratingly simple. To keep river banks from eroding, early farmers planted herbs along the side of the river. The roots grew long and held the muddy earth in place, ensuring the river doesn’t grow any wider, keeping crops safe. The engineers tried the same principle with their bridge foundation; if they can keep the sand from vibrating, the structure above it won’t sink.
Engineers inserted long metal rods into the sand where the foundation would stand, and that was it. Just like the herb roots, the steel rods kept the sand from shifting during earthquakes, making it as firm as any rock. The strangest part of it is, the rods aren’t even touching the solid floor or the base of the bridge.