Controversial Cure for Leaning Tower
(London Times 23 July 1998)
July 23 1998
Controversial cure for Leaning Tower
LETTER TO THE EDITOR
From Professor J. B. Burland, FEng, FRS
Sir, It is hardly surprising that any proposed intervention to stabilise the
Leaning Tower of Pisa will be controversial ("Experts wrangle over best angle",
report, July 18). Yet historical studies of its continued movements, coupled with
the most advanced analytical studies of its stability, show that the one certain
outcome if nothing is done is that it will collapse.
The proposed method of stabilising the tower is not, as the report suggests, to
"haul the tower back towards the upright with giant steel cables". It is the
extraction of soil from beneath the northern (high) side of the foundations,
thereby reducing the inclination in a gentle and controlled manner by an amount
that is imperceptible to the eye.
The sole purpose of the cables (which are temporary) is to provide a positive
method of holding the tower in the very unlikely event of unforeseen detrimental
movements. Not to provide such a safeguard system would indeed be highly
irresponsible.
The method of soil extraction satisfies all the architectural requirements of
restoration in that the history and character of the building are fully respected.
The method has been successfully used over the past four years to stabilise the
Metropolitan Cathedral in Mexico City which has undergone differential
settlements of over six feet.
The earliest known use of the method was by James Trubshaw in 1832 to
stabilise the Tower of St Chad in Wybunbury, Cheshire. Professors James
Beck and Piero Pierotti complain that the commission for the protection of the
tower has acted in secrecy.
I recommend that they, and anyone else interested in the tower, read my paper
published in the 1997 volume of the Journal of Architectural Conservation
where the work of the commission, including this proposed intervention, is fully
described and referenced.
Yours faithfully, JOHN BURLAND
(Member, Pisa Commission; Professor of Soil Mechanics),
Department of Civil Engineering,
Imperial College of Science,
Technology and Medicine,
Imperial College Road, SW7 2BU.
July 19.
Personal e-mail to:
gary@endex.com