Tower of Pisa losing its tilt

According to an annual report on the monument’s stability, the leaning Tower of Pisa has straightened up by an inch (2.5cm), due to stabilization efforts of the period between 1990 and 2001.

The first attempt at stabilization of the Tower was the injection of cement grout in the foundation in 1935 but it wasn’t successful inducing further lean. Later in 1993, lead ingots were used on the north side of the Tower’s base to counteract the southward tilt. Finally, soil excavation at the north part of the Tower proved to be the most reliable solution and the Tower had been straightened up by 44 cm in 2001. According to the paper Leaning Tower of Pisa: Behaviour after Stabilization Operations, later observations in the period between 2003 and 2008 indicate a reduction of the induced rate of northward rotation of the Tower and the rate of induced settlement of the centre of the foundation. Also, the drainage system stabilized the groundwater levels beneath the north side of the Tower’s foundation. The monument’s future shift cannot be definitely estimated but the authors of the aforementioned paper believe that even in the worst-case scenario it would take at least 200 years for the Tower to return to its previous inclination.

Source: MailOnline, Madrid Engineering Group