Tunneling Through Water
That is pretty much exactly what Dutch Engineers are doing to install a new subway system in Amsterdam. The city is built up on what amounts to mud in the first place, with structures supported on pile systems, essentially logs driven into the muck. Digging a new tunnels system through all that mud without destroying the fragile architecture is a real, daily challenge for the designers and the workers. They have come up with a novel way of checking for damage.
AMSTERDAM, Netherlands - Seventeenth-century masons built Amsterdam on a foundation of wooden poles planted in soggy, sandy ground, leaving behind a beautiful architectural museum — but one with walls prone to sinking or crumbling without warning. So how do you dig a subway under it?
Very carefully.
Construction of a new "North-South" line for this city of canals and rivers began in 2003, and is presenting Dutch engineers, famed for their ingenuity in keeping this waterlogged nation dry, with devilish challenges.
"The politicians told us: 'We want a subway, we're prepared to pay for it and accept some disruption, but the one thing we absolutely don't want is any damage to the city,'" said Johan Bosch, the project manager. "We need a system so that if things don't go as expected, we don't find out after the damage is irreparable."
The solution: 7,000 mirrors hung in clusters of three on buildings along the 2.4 miles of the route that's underground. Measuring devices shine infrared beams onto each mirror once an hour, measure the reflection, and feed data into a central computer.
After triangulating, the computer raises the alarm if any building shifts more than 0.5 millimeters in any direction. A millimeter is the thickness of a paper clip.
The system, unique on such a large scale, has already told townspeople something they may have guessed but couldn't know for sure: that theirs is a city in motion.
"We now know that whole segments of the city move by themselves, a number of millimeters over the course of a season," Bosch said.
Scheduled for completion in 2013, the $2.4 billion project stretches 5.9 miles in all and will transport an estimated 200,000 people daily, adding a new dimension to Amsterdam's traffic of bicycles, trams, cars, taxis, buses and boats.
It is actually a fascinating article, especially if you enjoy reading about amazing engineering. (It is a Yahoo link, so it is only going to be good for a couple of weeks.) They actually are going to excavate an underground canal, float a tunnels section into it and lower it into place. Tunneling in water. Amazing.
World news | Gaius Sunday, 22 July , 2007
By feeblemind, Sunday, 22 July , 2007 @ 3:34 pm
Call me skeptical. Engineering marvels aside, if this project mirrors similar public works projects in this country, they will never get it built for 2.4 billion and the projected 200,000 riders/day is likely wildly optimistic.
By Purple Avenger, Sunday, 22 July , 2007 @ 8:32 pm
If its a government project, it’ll cost’em $200B before all is said and done and it’ll leak like a sieve.