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Landslide Monitoring at the Cala Rossa … 127

Fig. 5 The inner giant joint upon the plateau of the west side of Cala Rossa

Fig. 6 Discontinuities plot of the
west side of Cala Rossa

the instability proneness. Especially where this joint set is The movements measured by the mechanical joint-meters
parallel to the slope face, it is possible to recognise an installed in the bay are generally lower than 1 mm (Fig. 10).
advanced lateral detensioning deformation process. Less Only eight measurement points showed variations over the
significance seems to have the sub-horizontal stratification 36 months exceeding 1 mm and only 1 is greater than 5 mm
planes. Taking into account the attitude of the main mea- (RE3M2, a joint in the central part of Cala Rossa).
sured joint, two failure mechanisms have been assumed for From the preliminary GPS data, consisting in the first
the movements in the front part of the cliffs: rock topples and survey performed in October 2012 and the following of May
rock wedge slides. 2013, April 2014 and July 2015 some horizontal millimeter
The results of the geomechanical analysis of the 20 sta- movements of the four unstable vertices may be observed,
tions, implemented in the GIS project, are showed in the but always inside the error ellipse and without an apparently
rock quality maps (Figs. 8 and 9) that constitute a prelimi- defined trend. Only for E2 and O2 vertices it is possible to
nary assessment of the rock fall susceptibility of the cliffs in observe a vertical millimeter movement, even if inside the
the study area. ellipse error, that denotes a presumable subsidence trend.