Saving the Tower of Pisa from collapse
Published on July 29th, 2010 | by Sevaan Franks1
Burland was convinced he had such a solution – a process called soil extraction – and ultimately he won over the rest of the committee. Akin to microsurgery, it entailed drilling out slivers of soil from beneath the northern side of the tower – away from the lean – and allowing gravity to coax the structure back upright. It had the advantage of not touching the tower itself, so keeping the art historians happy.
‘The pressure was immense, a modern wonder of the world was at stake – but I never doubted the logic of soil extraction,’ says Burland, cool as you like. As revealed in The Tower Restored, the procedure was actually pioneered in 1832 by Victorian engineer James Trubshaw on the leaning church-tower of St Chad’s in Nantwich.
Work began in 1999, using delicate, Archimedes-screw drills. At the same time, technicians in a piazza-site trailer monitored data from 120 sensors set up inside and beneath the tower.
Burland now came into his own. He had details of the tower and earth’s every movement faxed twice a day to his office in London (or to wherever he was on holiday – the prof remembers one frantic search for a fax machine while away with his wife in Syria). And after considerable number-crunching, he would advise how much drilling was necessary in the next 12 hours. By the time he called a successful halt, two years and 1,500 faxes later, 70 tons of soil had been removed and the tower had returned to its early 19th-century inclination.