The Leaning Tower of Pisa leans due to unstable ground and inadequate foundations. It did not collapse thanks to restoration work carried out to strengthen its structure and reduce its inclination.
From the start, the Leaning Tower of Pisa was built on foundations that were really too weak and too shallow to properly distribute its weight. As soon as the first three floors were completed, around 1178, the structure began to lean slightly to the south. The builders had planned for a foundation of about 3 meters, but clearly, this was not enough to support the expected 14,500 tons of marble. Added to this was the slow progress of the work, interrupted by wars, which allowed the base to continue to settle gently even before the upper floors could compensate for or correct the load. In short, the tower's leaning fate began early due to a poor estimate of the actual needs for structural integrity.
Under the Leaning Tower of Pisa, the ground is mainly made up of a soft and unstable mixture of clay, sand, and silt. This particular soil is very sensitive to changes in moisture: when it rains heavily, the clay swells and becomes unstable, and then during dry periods, it shrinks. As a result, the ground is constantly shifting beneath the tower, and very early in the construction, part of the soil began to sink under the weight. This uneven sinking phenomenon explains why the tower leans to one side rather than falling straight down. The problem is that the heavier the structure became with the addition of upper floors, the greater the tilt increased due to the continuous settling of this famous layer of water-saturated clay.
Over the centuries, several measures have attempted to prevent the Leaning Tower of Pisa from completely toppling over. As early as the 14th century, when it was already seriously leaning, engineers came up with the idea of constructing the upper floors offset, slightly curved in the opposite direction to compensate for the tilt. Much later, in the 19th century, more drastic measures were taken: they removed soil from the north side to slightly correct the balance and poured rough but effective concrete foundations around the base. Over time, strong steel cables and lead counterweights were also temporarily installed to stabilize the structure. Without these repeated interventions, Pisa's famous tilt would likely not be standing today.
Today, we continuously monitor the tilt thanks to electronic sensors installed in strategic locations of the tower. We also use ultra-precise lasers to detect any suspicious movement from a distance. To stabilize the structure, engineers carefully extracted controlled amounts of earth from beneath the foundation on the side opposite the tilt: it was risky, but it worked. In parallel, they installed lead counterweights to balance the entire structure and prevent the beautiful Italian tower from continuing its slow but certain fall. Today, thanks to these modern techniques, the tower moves barely a few millimeters per year, making it stable and safe for visitors.
The famous tilt is not a unique case: other buildings, such as the bell tower of St. Morand Church in Germany, also lean noticeably due to similar issues of unstable foundations.
The modern monitoring of the Tower uses highly sensitive instruments such as inclinometers and motion sensors to timely detect the slightest changes in its inclination and structure.
Do you know that the construction of the Leaning Tower of Pisa began in 1173 and lasted nearly two centuries? The work was often interrupted by conflicts and wars, which paradoxically allowed the ground to stabilize slightly between each phase of construction.
Despite its initial tilt, the Leaning Tower of Pisa has withstood several significant earthquakes thanks to its soft soil. Indeed, the clay in the subsoil, while responsible for the tilt, also acts as a natural shock absorber against earthquakes.
Yes, several buildings have a similar inclination, such as the Leaning Tower of Suurhusen in Germany or the Leaning Tower of Nevyansk in Russia, but none are as famous as the Leaning Tower of Pisa.
Since recent stabilization work, the tilt of the tower is no longer increasing significantly and it is constantly monitored using modern technologies.
Among the recent methods are excavation work beneath the foundation on the side opposite to the tilt to gradually restore its balance, and the use of cables and counterweights to secure the structure during the work.
Sure! Here’s the translation: "Yes, construction was interrupted for approximately a century due to political turmoil and the emergence of the initial tilt. This pause allowed the ground to partially stabilize and likely prevented the immediate collapse of the structure."
No, strict monitoring measures have been put in place, and stabilization work has significantly reduced the risk. Today, the Tower is safely open to visitors.
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