Over the last 30 years, Italy's iconic leaning Tower of Pisa has been helped back onto its feet by civil and structural engineers who have recently reduced its tilt by a further 4cm.
While that might not sound like much, it's in addition to the 43 cm engineers have shaved off its 4.5-metre-lean since the early 1990s. And the engineering team responsible says the Torre di Pisa is in better structural shape than expected, assuring its presence under the Tuscan sun for hundreds of years to come.
Generations of engineers constructed the 14,500 tonne 60 mere-high bell tower between 1174 and 1399. The structure had started to lean during construction due to the soft clay and sandy soil it was built on. Constructed of white marble in the medieval Romanesque style, it has eight stories including the bell chamber, and two internal spiral staircases. Its much larger neighbours, the Cathedral of Pisa and Bapistry, are also sinking.
Over its +600-year lifetime, the Tower of Pisa began sinking more to one side and, by the late 20th century, it had sunk close to four metres into the ground. Some remediation had been carried out in the 1920s by injecting cement grouting into the foundations to stabilise it, however, by 1990 the tower had reached critical status.
It was closed to the public for more than a decade while engineers provided support and attempted to reduce the tilt of their medieval predecessors' handiwork. If ever there was an argument for ongoing Professional Development (PD) for engineers, this is it.
In the early 90s, lead weights were applied to the high side of the structure and soil was siphoned from beneath the tower's foundations under the high side via 12 bore holes. They extracted around 37 mᶟ of soil and the tower responded, so the weights were gradually removed.
The structure was re-opened to the public in 2001 and, without having undergone further remediation, the Tower of Pisa hasn't needed to lean on its supportive engineers quite so much anymore, except to check on its structural health.
Image: The not-so-leaning Tower of Pisa now stands that much taller. Source: Pixabay.