The Leaning Tower of Pisa: Kinematic Levelling of the Foundation Plane in the Period 1993–1994

The aim of this paper is to analyse kinematically the rigid tilt of the Pisa Tower foundation plane in the period 1993–1994, when a counterweight was displaced on the North side of the basement. The kinematics is studied using a kinematic levelling approach. In the first four paragraphes the kinematic levelling method and the counterweight application history are briefly described; moreover the results obtained are briefly analysed with some closing remarks. The eight benchmarks under study are hanged to the Tower inside walls and can give a good idea of the Tower basement deformation trend. The levelling measurements have been made daily since 14/06/1993 and this fact allows to use these informations as a valuable way to check the reliability of the electronic instruments that observe continuously the Tower behaviour.