September 24, 2021

I, Science

The science magazine of Imperial College

Earlier this year, Imperial College Professor, John Burland travelled to Italy to celebrate the 20th anniversary of a project that prevented the Leaning Tower of Pisa from collapsing. Professor Burland worked as part of a 14 member committee charged with stabilising the tower, which began to develop its characteristic lean after construction progressed to the second floor in 1178. The professor of soil mechanics worked for 11 years on the project to save the tower, which saw 38 cubic metres of soil removed from underneath the raised end of the tower, thus returning it to a position previously seen in 1838.

Professor Burland and his colleagues subsequently discovered that extracting the soil in this way corrected some of the tilt, but it did not stop the tower from leaning more each year. After years of further research, they discovered that the south side of the water table was higher than on the north side. Consequently, in winter, when it poured with rain, the water table rose, lifting the tower each year in increments. The team rectified this problem by installing drains to control the water table beneath the north side. In May 2008, the engineers finally announced that that tower had been stabilised and that they had stopped the building from moving for the first time in its history.

Professor Burland spoke of his work to save the iconic tower in a special documentary for the BBC’s The One Show, saying “it is amazing to see the tower restored to its former glory…[it] is one of the proudest achievements in my career.” Professor Burland has also worked to ensure the stability of the Big Ben Clock Tower and was London Underground’s expert witness for the Parliamentary Select Committees on the Jubilee Line Extension.

Image from Piazza de Maricoli from