As the bell tower of Pisa Cathedral, 1 173 was designed to stand vertically when it was built on August 9, 1973. It was originally designed to be 8 floors and 54.8 meters high. Its unique white shining medieval style building will be one of the most noteworthy bell towers in Europe, even if it does not tilt later.
Why the leaning tower of Pisa leans has been debated by experts. Especially in the14th century, people are wandering between two arguments, whether the leaning tower of Pisa is the result of the cumulative effect of unpredictable and unavoidable ground subsidence in the construction process, or whether the architect deliberately did it.
In the 20th century, with the more and more accurate measurement of the leaning tower of Pisa, the in-depth survey of foundation soil with various advanced equipment and the study of historical archives, some facts gradually surfaced. The leaning tower of Pisa was supposed to be a vertical building in its original design, but it began to deviate from its correct position at the early stage of construction.
In 1 178, when the bell tower was built to the fourth floor, it was found that the bell tower had tilted to the southeast due to uneven foundation and soft soil, so the project was suspended.
During the period of 1 198, the existence of the bell tower was recorded, which indicated that although the bell tower was tilted, at least one bell was hung, realizing its original intention as a bell tower.
123 1 year, the project continued, and marble was recorded for the first time in the bell tower. The builder took various measures to correct the inclination, and deliberately built the upper floor of the bell tower as an inclination in the opposite direction in order to compensate for the deviation of the center of gravity that had occurred.
When 1278 progressed to the seventh floor, the tower was no longer straight, but concave. The project was suspended again.
1292, Giovanni Pisano measured the inclination of the bell tower with a plumb line.
According to the existing written records, the leaning tower of Pisa has been inclined slowly for centuries, and it has actually reached a certain degree of balance with the soil under its foundation.
At the end of the third floor in the first stage of construction, the clock tower is tilted about1/4 to the north.
In the second stage, due to excessive rectification, the seventh floor of 1278 was tilted to the south by about 0.6.
1360 increased to1.6 when the top-floor clock house was built.
18 17, two British scholars, Cresy and Taylor, measured the inclination with a plumb line, and the result at that time was 5.
The survey of Giorgio Vasari in 1550 was 267 years apart from the survey of Cresy and Taylor in 18 17, and the tilt only increased by 5 cm. Therefore, people have not carried out special maintenance on the leaning tower.
1360, after almost a century of stagnation, the bell tower began its last sprint to completion and made the last important revision.
1372 The top floor of the clock was completed. The 54-meter-high 8-story bell tower has seven bells, but it has not been knocked because it is in danger of collapse at all times. And it keeps falling downward.
The leaning tower of Pisa is inclined because of the particularity of the soil layer under its foundation. Under the leaning tower of Pisa, there are several layers of soil with different materials. The sediments of various soft silt and very soft clay are alternately formed, and the groundwater layer is about one meter deep. This conclusion is obtained after observing the composition of foundation soil layer. The latest excavation shows that the bell tower was built on the edge of the ancient coast, so the soil was desertified and sunk when it was built.
However, a project in 1838 led to the sudden acceleration of the leaning tower of Pisa, and people had to take emergency maintenance measures. At that time, Alessandro della Gherardesca, an architect, excavated around the original sealed leaning tower foundation to explore the shape of the foundation and reveal whether the cylindrical column foundation and foundation steps were the same as expected. This behavior made the leaning tower lose its original balance, the foundation began to crack, and the most serious phenomenon was the influx of groundwater. The survey results after this project show that the tilt has increased by 20 cm, while the total tilt in the previous 267 years was only 5 cm.
After the completion of the project of 1838, the accelerated inclination of the leaning tower of Pisa continued for several years, and then stabilized, and decreased to about 0. 1 cm per year. The tower deviated from the "natural posture" for more than 5 meters.