ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

configuration through the analysis of many drainage basins
of Italy, located in areas having different tectonic histoires
and various and complex geomorphological characteristics.
The result of extensive inquiries have shown that the
relations under study can be quantitatively expressed by
regression equations connecting the hypsometric integral
values (Jv), which synthetically express the present planoaltirnetric
configuration of drainage basins, to the values of
some geomorphic parametres which describe the morphogenetic
process spreading and effectiveness. In particular,
the chosen parametres express - in connection with the
drainage basin area (A) - the total lenghts of deepening
streaan channels (LeiA), the area affected by sheet, rill and
gully erosion (AdIA), the area affected by mass moyement
(AmIA), the amplitude of relief (RIA) and the extention
of alluvial deposits (AllA).
This kind of analysis has been applied to a statistically significant
set of drainage basins of Central Italy; they have been
chosen taking into account their different geological and
morphological conditions as well as their geographicallocation
on the Adriatic or Tyrrhenian side. The statistical
analysis of the relations between the hypsometric integrals
and the geomorphic'parametres confirmed the close interdependence
between the dependent and independent variables.
Moreover the results obtained have shown that some
interesting differences exist between the behaviour of
the drainage basins of the two different sides of the Italian
peninsula. More in details, the drainage basins of Central
Italy which join the Adriatic Sea show plano-altimetric configurations
characterized by integral low values; denudational
processes, and slope processes in particular, are usually
widespread and effective. The drainage basins of the
Tyrrhenian side of Central Italy show a quite different situation;
they are generally affected by denudation processes
which are less spread and intense, although their hysometric
curves have often integral low values. However, if partial
basins affected by local structural conditions are considered
the relations between integral low values and the type
and intensity of denudational process is still verified.
Actually, it seems likely that the general plano-altimetric
configurations of the drainage basins of Central Italy can
be explained in different ways: the interpretation of hypsometric
curves as function of the complexity of denudational
processes and of the rate of geomorphological changes
is surely more suitable in the case of the basins of the
Adriatic side, while the Strahler's classic interpretation, in
terms of stage of the geomorphic cycle, is generally more
suitable for the basins of the Tyrrhenian side. This different
behaviour can be framed into the recent tectonic of
the central part of the Italian peninsula. Starting from Upper
Pliocene, the Adriatic side was mainly affected by
uplifting which resulted in an enhanced effectiveness of
morphogenetic processes. On the Tyrrhenian side, instead,
more ancient Horst and Graben tectonics prevailed which
was more favourable to the ahievement of a more advanced
stage in the geomorphic cycle.
Finally, the hypsometric analysis showed to be useful also
to single out within the same basin the presence of areas
which have undergone tectonic events of different kind and
intensity.
LEANDRO D'ALESSANDR0 1
, RiNALDO GENEVOIS 2
,
MATTEO BERTI 2, PIA R. TECCA 3 & ALESSANDRO URBANI 1
Stability analises and stabilization works of the
Montepiano travertineous cliff (Central Italy)
1Dipartimento di Scienze della Terra, Universita di Roma,
p.le A. Moro, 00185 Roma, Italy
2 Dipartimento di Scienze della Terra e Geo-Ambientali,
Universita di Bologna, via Zamboni 67, 40127 Bologna, Italy
3 Cnr-Irpi di Padova, corso Stati Uniti 4, Padova, Italy
The paper relates results of the research carried out on the
instability phenomena of a travertine plate resting on overconsolidated
plio-pleistocenic clayey silts and silty clays
through some thin beds of sands and conglomerates.
The travertine plate sets up a vertical face about 30 m high,
marked by a sequence of arch-shaped features which result
from the geomorphological evolution occurred mainly by
means of rotational sliding and lateral spreadings. The edge
of the travertine plate is strongly fissured: the main fractures
set is parallel to the travertine face and concerns the
whole thickness of the plate. As a matter of facts, the travertine
behaves as a rigid plate resting on the underlying
plastic silty clays; tension cracks develop at the boundary
of the plate itself and cause the separation of large blocks
of travertine. The lowering and/or the rotation of these
blocks cause instability mechanisms of different type: the
geomorphological evolution of the cliff has occurred, in
fact, mainly by means of landslides phenomena classificable
as lateral spreadings and rotational sliding.
The comparison of the geomorphological features at the
present time existing and historically delineated before the
last catastrophic event testify for the present activity of the
same fractures sets and for the critical state of the cliff. The
geotechnical and geomechanical characteristics of the outcropping
material have been then characterized by means
of field surveys, site investigations and laboratory tests
with the aim to design the suitable consolidation works
due to the high risk connected to a landslide phenomenon.
A detailed geological and geomorphological mapping has
been realized before the subsurface exploration programme
was carried out by means of geophysical surveys and
mechanical boreholes.
The stability analyses have been carried out using a finite
differences code that shows the present state of stresses
and strains in the whole slope. This technique is more
complex than the conventional limit equilibrium methods,
but it nevertheless can provide a detailed insight into the
way that a slope will deform and fail and therefore provide
a valuable addition to methods of analysing slope behaviour.
The effectiveness of the proposed consolidation
works has been tested afterwords using the same computer
program with the new morphological and hydrogeological
conditions. The control of subsurface water and the alteration
of the slope geometry result to be, in fact, the only suitable
methods of stabilization of the slope.
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