Engineers dig in to save leaning tower of Pisa

The leaning tower of Pisa has been saved from the imminent threat of collapse. An elaborate engineering operation has almost reversed the tilt of the tower to the angle it was at 162 years ago, scientists told the British Association meeting yesterday.

The leaning tower of Pisa has been saved from the imminent threat of collapse. An elaborate engineering operation has almost reversed the tilt of the tower to the angle it was at 162 years ago, scientists told the British Association meeting yesterday.

Using expertise gathered during attempts to ensure that Big Ben did not topple over during excavation of Westminster's new Tube station, British scientists have helped Italian engineers reverse an 800-year tilt that was about to bring down the world's most famous tower.

Professor John Burland, a civil engineer at Imperial College in London and one of two foreign members of the commission set up to save the tower, said the halfway point had been reached in reversing the tilt to the point it was at in 1838.

"It's too early to be triumphant, but it's looking good," he said. "We're hoping to reduce the inclination of the tower by half a degree and at present it's leaning at 5 degrees. It means bringing the top back by about 45cm. We've brought it back by a little over half, about 23cm."

Professor Burland said that in 1838 an architect had dug a walkway around the tower, causing it to lurch by about a quarter of a degree.

"We're nearly back to 1838 and now nibbling into what this mad architect did, and then we'll stop," he said.

Civil engineers are drilling under the northern foundations of the tower to extract soil. As the soil is removed, the foundations sink slightly. About half of the 30 tons to be removed has already been excavated.

Professor Burland said: "We're aiming to finish soil extraction in the new year and the politicians hope to reopen [the tower] in 2001 in time for the feast of San Renieri, the patron saint of Pisa, on 16 June."

Excavation work resumed this week after stopping forItaly's August holiday. The top of the tower is now being movedat a rate of 1.4mm a day.

But when the work is complete, the tower will still be leaning, the professor said. "It will still hit you in the pit of the stomach as you approach it."

Professor Burland worked on the construction of an underground car park for MPs at Westminster in the 1970s and on the recent rebuilding of Westminster Tube station, which involved digging a 40m-deep pit next to Big Ben.

"What we've done to stabilise the Pisa tower is the mirror image of what we did with Big Ben. Instead of pumping grout into the ground, we did the reverse with Pisa, where we've been extracting soil from the high side," he said.

"Pisa is the ultimate civil engineering challenge. It was on the point of falling over because it was on very, very soft ground. It was moving inexorably to the point where it was about to collapse," he told the week-long conference. "The one thing we could be sure that would topple it over was to do nothing. Reopening the tower to the public should be safe. The hope is that the public would be allowed up the tower. The tower weighs 14,500 tons and visitors effectively make no difference at all."