Archive for December 14th, 2010

Leaning Tower of Pisa cleaned and stabilized

Tuesday, December 14th, 2010

The Leaning Tower of Pisa in 1992 (left) and today (right)The 8-year restoration of the famed Leaning Tower of Pisa is finally complete. The medieval bell tower is now stabilized and clean for the first time in centuries. It needed a lot of work, thanks to tourists and their endless need to mark their presence, plus their pawing the walls to climb the wonky staircases, pollution, pigeon guano and corrosive sea salt. When the tower was built Pisa was on the coast. Then its port silted over and today the city is 7 miles from the sea, but salt is still blown by the wind and rain and the lean has made efficient drainage impossible.

Restorer cleans a figure with a syringe and gauzeRestorers cleaned every single stone in the structure with chisels, lasers and syringes. Yes, syringes. When you realize 10 people had 24,424 blocks of stone to clean with syringes, all of a sudden 8 years and 3 months doesn’t seem like all that long a time. The lean also made restoration extremely physically challenging since restorers had to work at an angle all day and sometimes at night too. They even invented a new kind of scaffolding to get it done.

The building’s circular structure and the unstable surrounding terrain meant traditional scaffolding for the restoration was not an option, so engineers designed a unique aluminium framework that compensated for the tower’s lean.

“We get a team of mountaineers in to move the scaffolding from floor to floor,” said head engineer Giuseppe Carluccio, from BCD Progetti in Rome.

“They’re fantastic, these kids are passionate about climbing, know how to use their ropes, but most importantly, aren’t afraid of heights!” he said.

The mountaineers moved the scaffolding gradually up the tower to the last floor and will return one more time to take it down for good.

The last scaffolding layer is due to be taken down early next year.

The stabilization part of the project was finished in 2008. Engineers removed 70 metric tons of earth from underneath the taller northern side of the tower, stopping its movement for the first time since 1178. It is now 19″ straighter, and leans at a 3.99 degree angle instead of the 5.5 degree angle it was leaning at before it was closed to tourism for 11 years in 1990.

Construction on the tower began in 1173. By the time the 3rd story was built in 1178, the tower was beginning to sink due to a flimsy 3-feet-deep foundation set in soggy subsoil. A series of wars stopped construction at that time and no further work was done on the tower for another 100 years, which turned out to be a blessing in disguise because if they had kept going chances are the tower would have collapsed. The century of rest gave the subsoil time to compact and stabilize itself enough to support 4 more floors and a belfry. When construction resumed in 1272, engineers compensated for the lean by building one side of each floor taller than the other.

So to recap: it leans, most of the floors are taller on one side than on the other, it’s covered in pigeon crap and human effluvia, and the arches leave it entirely open to the elements, from driving salty rain to beating summer sun. Those restorers deserve a medal.

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