Weathering characterization for landslides modeling in granitoid rock masses of the Capo Vaticano promontory (Calabria, Italy)

This work focuses on developing multidisciplinary researches concerning weathering profiles related to landscape evolution of the Capo Vaticano promontory on the CalabriaTyrrhenian side (southern Italy). In this area, the tectonic uplift,occurred at least since Pleistocene, together with the Mediterranean climatic conditions, is the main cause of deep weathering anddenudation processes. The latter occurred on the outcroppingrocks of the crystalline-metamorphic basement, made up ofweathered granitoids, in turn belonging to the Monte Poro granitoid complex (intermediate to felsic plutonic rocks covered byCenozoic sedimentary successions). Field observations coupled toborehole explorations, geophysical surveys, and mineropetrographical analyses allowed the characterization of the granitoid outcrops typical of the studied area in terms of kind anddegree of slope instability. This characterization was based onsuitable correlations verified between several factors as weatheringdegree, elastic properties of rocks, and discontinuity features.Weathering profiles are mainly composed by rock masses varyingfrom completely weathered rock with corestones of highly weathered rock (classes IV–V) to slightly weathered rocks (class II). Theweathered rocks are involved in several landslide typologies suchas debris flow (frequency 48.5%), translational slide (frequency33.3%), and minor rock fall and rotational slide (frequency 9%).The achieved data allowed the establishment of a general correlation between weathering degree and type of slope instability.Debris flow-type instabilities are predominant on the steeperslopes, involving very poor rock masses ascribed to the shallowestportions of the weathering class IV. Translational slides are lesswidespread than the previous ones and often involve a mixture ofsoil and highly weathered rocks. Rotational slides are more frequently close to the top of the slopes, where the thicknesses ofmore weathered rocks increase, and involve mainly rock massesbelonging to the weathering classes IV and V. Rock falls mostlyoccur on the vertical escarpments of the road cuts and are controlled by the characteristics of the main discontinuities. Theassessment of rock mass rating and slope mass rating, based onthe application of the discontinuity data, allowed respectively anevaluation of the quality of rock masses and of the susceptibility ofrock slopes to failure. The comparison between the last one andthe real stability conditions along the cut slopes shows a goodcorrespondence. Finally, the geological strength index system wasalso applied for the estimation of rock mass properties. Theachieved results give a worthy support for a better understandingof the relationship between the distribution of landslides and thegeological features related to different weathering degrees. Therefore, they can provide a reliable tool to evaluate the potentialstability conditions of the rock slopes in the studied area and ageneral reference framework for the study of weathering processesin other regions with similar geological features.