The Leaning Tower of Pisa in Italy is known for its inclination and has been the subject of speculation and concern for many years. Despite enduring four earthquakes and significant movement, the tower remains standing. Its iconic lean has garnered widespread attention and fascination.
Engineers and other experts have worked to prevent the Leaning Tower of Pisa from collapsing for a long time, and their efforts have paid off. According to a recent survey, the tower has straightened out slightly over the past two decades, rising about 4 centimeters (1.6 inches). This survey was conducted by a group of geotechnical engineers and funded by Opera Primaziale Pisana, a non-profit organization responsible for preserving the historic site. Despite its age (850 years) and significant tilt (5 meters), and subsidence (over 3 meters), the tower is in good condition, according to an Opera Primaziale Pisana spokesperson.
Restoration Efforts
The construction of the Leaning Tower of Pisa began in 1174, but it was soon clear that there were problems with the structure. The shallow foundations, built on unstable ground composed of mud, sand, and clay, caused the tower to lean to one side. To correct this lean, the engineers working on the tower made the upper floors taller on one side, contributing to the tower's distinctive curved and lopsided appearance. Over the years, the lean of the tower continued to increase, and various attempts were made to stabilize the structure. By the 1990s, the tower had a 5.5-degree lean to the south, beyond the point at which experts believed it would collapse.
In response to the tower's increasing lean, the Italian government closed it to the public and assembled a team of experts, led by civil engineer Michele Jamiolkowski, to devise a plan to save it. One idea was to inject cement beneath the tower, which was deemed too risky. Instead, the team decided to anchor the north side of the tower with 900 tons (816 metric tonnes) of lead weights to counterbalance the sunken south side.
When the lead weights failed to improve the tower's stability, the team decided to remove soil from beneath the north side of the tower. This caused the tower to rise and rotate. The stabilization project, which took place over a decade, was completed in 2001. As a result, the tower straightened out by about 40 centimeters, and its current tilt is about 4 degrees, which is still twice as much as the original lean when the tower was completed in 1350. In 2013, researchers from the CSIRO, Australia's national science agency, used 3D scanners to create detailed digital reconstructions of the tower, which could be used for repair work if necessary.
Pisa's 'Leaning' History
Despite its history of instability, it is unlikely that the Leaning Tower of Pisa will collapse soon. According to geo technician Nunziante Squeglia, a professor at the University of Pisa who is part of the monitoring group, the tower sways very slightly, moving on average about half a millimeter per year. While the tower's stability is important, Squeglia has said it is in better condition than expected. The Leaning Tower of Pisa is not the only historic structure in Italy that is being closely monitored for the risk of collapse.
Scientists have been studying cracks in Michelangelo's statue of David for centuries, and their concerns have been heightened by a 2014 paper that found that a 5-degree tilt had already caused damage and could eventually lead to the statue's collapse. Earthquakes in 2014 also raised concerns about the statue's stability.
According to experts, the Leaning Tower of Pisa should be stable for at least the next 300 years and possibly even longer. Some engineers believe the restoration efforts could be so successful that the tower may eventually straighten out completely. Ironically, the soft soils beneath the tower's foundation, which caused it's characteristic lean, may now offer some protection from earthquakes, allowing the structure to vibrate for a longer period without being destroyed. While the future of Michelangelo's statue of David is uncertain, the Leaning Tower of Pisa is expected to remain standing for the foreseeable future. If it eventually stands up straight, it is unclear what will happen to its name.
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