72
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
The possibilities offered in this field by technological
progress in Geotechnical Engineering in recent years have
stimulated these activities all over the world, as is shown by the
reports published in journals and in conference proceedings. Of
course the potential of the new technologies opens up
fascinating prospects in this sector; suffice it to think of the
possibilities of introducing structural elements of any size into
the soil or of mixing the soil with cement to turn it into a new
coherent material that is very similar to concrete, or of injecting
hardening materials that replace pore pressure fluids in
predetermined points of the subsoil, using probes of all lengths
that can travel in any direction, even along predetermined and
controlled, curved lines.
Actually, scientific progress and the great potential and
flexibility of Geotechnical Engineering technology have
allowed for the conservation and protection of important
historic sites threatened by instability, landslides and weathering
of the soils on which they rise.
Suffice it to mention the measures taken to protect Orvieto,
Italy (Fig. 1), that took more than a decade, with the anchoring
of the high cliff faces made of soft pyroclastic rock (tuff) whose
stability had been undermined by the slow softening of the
Pliocene overconsolidated clays, present at their base
(Manfredini et al. 1980, Martinetti 1981, Lembo Fazio et al.
1984, Tommasi et al. 1997, Tommasi and Ribacchi 1997, Pane
and Martini 1997, Tommasi et al. 2005, Soccodato et al. 2013)
a)
b)
Figure 1. Orvieto: the tuff high cliff (a) consolidated by means of
passive anchors, nails and drain pipes (b). Scheme of the strengthening
works along the edge of the Rock (Cencetti et al., 2005).
Not as extensive but not less important are the anchorage
works on another cliff face overlooking Lake Maggiore thanks
to which the historic hermitage of Santa Caterina del Sasso (Fig.
2) has been saved (Balossi Restelli 2009). More recently, a set
of fiberglass tie-rods and a masonry underpinning have stopped
the collapse of large tuff blocks from the NW face of the
Palatine Hill. This measure not only made it possible to stop the
progressive instability caused by the erosion of the sand levels
and by the excavations made during the Middle Ages, but also
to free the stone face from the debris produced by the collapsed
rock and discover the unsuspected presence of Hypogeums
(Tomei and Filetici 2011).
New intervention arose also from the progress achieved in
the last decades in the knowledge of the behaviour of
unsaturated soils and in the measurement of soil suction.
Actually many old buildings with shallow footings suffer the
effects of the shrinkage and swelling of unsaturated cohesive
soils. The climate changes which occur in some world areas or
the water level decrease produced by intense pumping lead
often to new unattended settlements. However, as it has been
recently proposed and implemented, control system of the
saturation degree of the foundation soil can be carried out by
means of subsurface porous water pipes, to be driven according
to prearranged profiles (Carbonella et. al 2011).
a)
b)
Figure 2. a) The limestone cliff over the hermitage of Santa Caterina del
Sasso. b) The anchoring consolidation works.
3 A MORE RESPECTFUL APPROACH: PRESERVING
THE KNOWLEDGE OF THE PAST
Quite often, for most engineers, the interaction between
Geotechnics and the protection of ancient buildings is seen only
from the standpoint of the design and execution of consolidation
measures. First of all it has been noticed that measures taken to
improve the static behaviour or seismic resistance of ancient
buildings have not always had lasting effects, but on the
contrary they have often produced even greater and irreversible
damages. One example speaks for all: the Minaret of Mosul,
Iraq, UNESCO Heritage monument (Fig. 3). The heavy,
invasive, structural consolidation (by means of iron nails) and
underpinning (micropiles) carried out in the 1981 (Lizzi, 1982,
1997) have not protected the monument from a further
worsening of its static conditions, so much so that new
