Leaning Tower of Pisa is straightening up

The Leaning Tower of Pisa is slowly straightening thanks to engineering works carried out in the 1990s to stop it toppling.

The bell tower’s tilt has been corrected by four centimetres since 2001.

The Leaning Tower of Pisa is slowly straightening thanks to engineering works carried out in the 1990s to stop it toppling over, experts said.

The bell tower’s tilt has been corrected by four centimetres since 2001, said the team, which monitors the structure every three months. “It’s as if it has had two centuries taken off its age,” Salvatore Settis, one member, said. Nunziante Squeglia, a professor of geotechnics at the University of Pisa who works with the experts, added: “What counts the most is the stability of the tower, which is better than expected.”

After construction of the 56m tower started in the 12th century, builders quickly realised that the soft ground was causing it to lean over precariously, prompting them to build the upper floors with one side higher than the other to compensate.

As centuries passed, the tower, which weighs more than 14,000 tonnes, reached a 5.5-degree lean — more than four metres at the top. By 1990 the lean was increasing by about 1.5mm a year, leading to fears that it would fall. Engineers moved in and removed large amounts of earth under the higher north side. They also drained groundwater after it was discovered that the water table was higher that side, exacerbating the lean. Six hundred tonnes of lead ingots were placed on the raised foundations of the north side to push them down, while steel cables were used to halt the slow toppling of the tower.

By 2001 the operation was declared a success after the tower’s lean was reduced by 41 centimetres. This week the experts found that the correction was still working, with another 4cm reduction measured in the lean in the past 17 years.

Professor Squeglia said the movement was so slow that it would take 4,000 years for the tower to stand upright. He added that the engineering work could have a temporary effect and the building could once again start leaning. “That,” he said, “is another story.”

— The Times