Leaning Tower of Pisa: Behaviour after Stabilization Operations

John B. Burland, Michele B. Jamiolkowski, Carlo Viggiani

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It is well known that the foundations of the Leaning Tower of Pisa were stabilised using the method of underexcavation to reduce the southward inclination of the Tower by about 10 percent in combination with controlling the seasonally fluctuating water table beneath the north side. Having been closed to the public since early in 1990, the Tower was re-opened in December 2001. The paper summarises the response of the Tower during the period of implementation of the stabilisation works. Monitoring of the movements of the Tower has been continuing and the observations obtained since 2001 are presented. It is shown that over the six years between 2003 and 2008 the induced rate of northward rotation of the Tower has been steadily reducing to less than 0.2 arc seconds per year. Similarly the rate of induced settlement of the centre of the foundation has been steadily reducing and is approaching the background rate of settlement of the Piazza. Piezometer measurements close to the north side of the foundation shows that the drainage system has been successful in stabilising the groundwater levels beneath the north side of the Tower’s foundation. The paper concludes with a brief discussion on the possible future behaviour of the Tower.


Leaning Tower of Pisa, leaning instability, stabilization works

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