73
Honour Lectures /
Conférences honorifiques
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
measures are most urgent, but it is extremely difficult and
problematic to decide on how to go about such measures.
Figure 3. The Minaret of Mosul, underpinned micropiles and
structurally strengthened in 1981 (Lizzi 1982, 1997).
The role of Geotechnical Engineers in the conservation of
historic towns and monuments could be much broader and
multifaceted and even more attractive in cultural terms than
what is generally believed. The general perception of
geotechnical engineering only as a means for intervening in a
historic structure from the static standpoint is restrictive and far
from the present view of thinking about monument
conservation. Indeed it is now common thinking that the
replacement or substantial modification of a structure or of a
foundation alters or even eliminates forever an historically
essential feature of a monument, the idea being that even its non
visible parts, like the foundations, must also be preserved as a
material token of its history.
A self evident example of the changing of mind that
occurred in the course of a few decades is provided by the
Leaning Tower of Pisa: for a long time, faced with the objective
difficulty in interpreting the phenomena that were causing the
progressive inclination of the Tower, technological solutions
were offered that were intended to make the Tower independent
of the behaviour of its foundation soil. In 1962, F. Terracina, a
geotechnical engineer who was a passionate scholar of the
Tower, published a proposal (Fig. 4) that simply envisaged the
removal of soil from the uphill section (anticipating the solution
adopted 40 years later) (Terracina 1962), but its suggestion
remained unattended.
Figure 4. Layout of the underexcavation proposed by Terracina (1962).
Geotechnical Engineering had made great progress (with the
development of micropiles and consolidation techniques) and
the call for projects launched to save the Tower in 1973, after
the completion of the studies on its subsoil (Cestelli Guidi et al.
1971) attracted only projects that aimed at creating a deep-
seated underpinning (Fig. 5), across soils that were more or less
deformable (Burland et al. 2013).
a)
b)
Figure 5. Some of the intervention measures proposed to save the Tower
of Pisa at the 1973 call for projects (Burland et al. 2013): a) Fondedile
proposal; b) Impredit-Gambogi-Rodio proposal.
Actually until the early 1990s, the concept that the
conservation of a monument involves also saving its
construction components, even those that are not visible had not
yet gained ground; the idea that the Tower of Pisa, once it were
to be transferred onto a new foundation built using the
technologies of the 20th century, would become a fake, only a
pure icon of the monument, was not understood (Calabresi and
Cestelli Guidi 1990, Calabresi 2011). The new way of thinking
made its way gradually and radically changed the cultural
approach to the consolidation of ancient buildings, and in the
case of the Tower of Pisa, it led to the solution that was finally
and happily adopted for its stabilization (Burland et al. 2000).
4 THE NEED OF MULTIDISCIPLINARY STUDIES
If the protection of a historic and monumental building has the
aim of maintaining and spreading the knowledge of past eras
and civilizations, then the study of the interaction between
buildings and the environment, and in particular their
foundation soils, brings a substantial contribution to it; it may
help understand the choices made by the designers at the time of
construction, the changes that occurred over the years, the
causes of damages, and the techniques and materials used and
relate them to the natural and artificial materials available, to
the machines and to the historic context. All this helps deepen
our knowledge of remote times. In this setting the contribution
offered by Geotechnics, alongside that offered by structural
engineers, geologists, seismologists, architects, art historians
and construction historians may play an extremely important
role. The examples of activities carried out with this spirit are
now a great many and have been quite successful with at times
unexpected and surprising results. More than thirty years ago
the archaeologist Gullini had already presented a fascinating
picture of the results achieved through cooperation between
geotechnical engineers, archaeologists and historians in
studying the developments in construction techniques and
design in antiquity (Gullini 1980). They studied the foundations
of ancient monuments and archaeological settlements in
Mesopotamia and in the Mediterranean area from the 4
th
millennium B.C. to the late Roman Empire. Today there are
many conservation projects sponsored by UNESCO which have
a multidisciplinary approach in which Geology and Geotechnics
play an essential role: for instance mention can be made of the
set of measures proposed for Greece presented by IAEG
(Christaras 2003).
An Italian example is the Valley of the Temples in
Agrigento (Croce et al. 1980.): studies carried out on the slope
stability of the area where the temples rise have contributed to a
better understanding of the history of Magna Greece and of the
technical culture of its inhabitants between the 6th and 5th
centuries B.C. within the frame of our knowledge of ancient
Greece architecture (Dinsmoor 1975).
