In 1993, 650 tons of lead were hanged from the North side of the building, which stopped the leaning from increasing for a while. In 1987, the tower was declared a part of the Piazza dei Miracoli UNESCO World Heritage Site. In 1995, an attempt was made to expand the foundations under the south side of the building. The ground was frozen using liquid nitrogen, to stop it from moving. Stones were removed from the tower in order to insert metal rods. However, it was not known that the removed stones were part of the original foundation of the building. In one night, the lean increased as much as it normally would over 2 years. 250 tons of lead were quickly added. A British engineering professor came up with the idea of removing ground soil from under the high side of the tower instead of trying to strengthen the low side by adding to its foundation. Work began in 1999 and was done extremely slowly so that the tower wouldn't get a sudden shock. When the work was completed, at the beginning of June 2001, the tower had been straightened by about 16 inches, which was its position way back in 1838. In May 2008, after the removal of 70 tons of earth, the tower had stabilized. The engineers estimated that the tower would be stable for at least the next 200 years.
In 1993, 650 tons of lead were hanged from the North side of the building, which stopped the leaning from increasing for a while. In 1987, the tower was declared a part of the Piazza dei Miracoli UNESCO World Heritage Site. In 1995, an attempt was made to expand the foundations under the south side of the building. The ground was frozen using liquid nitrogen, to stop it from moving. Stones were removed from the tower in order to insert metal rods. However, it was not known that the removed stones were part of the original foundation of the building. In one night, the lean increased as much as it normally would over 2 years. 250 tons of lead were quickly added. A British engineering professor came up with the idea of removing ground soil from under the high side of the tower instead of trying to strengthen the low side by adding to its foundation. Work began in 1999 and was done extremely slowly so that the tower wouldn't get a sudden shock. When the work was completed, at the beginning of June 2001, the tower had been straightened by about 16 inches, which was its position way back in 1838. In May 2008, after the removal of 70 tons of earth, the tower had stabilized. The engineers estimated that the tower would be stable for at least the next 200 years.
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