Geotechnical subsoil modelling of a slope from the interpretation of ambient noise measurements and 2D site response analyses

Abstract

Within the context of seismic risk assessment, the prediction of the dynamic response of natural slopes is strictly related to the accurate definition of the geotechnical subsoil model. This aspect is particularly challenging for those slopes characterised by the presence of buried morphologies, for which the vertical and lateral heterogeneities of the subsoil setting may predispose them to additional risks during seismic events. The paper proposes a methodological procedure aimed at identifying preliminary subsoil models of areas characterised by uneven topography and buried lithological bodies of uncertain morphology, through the comparison of parametric site response analyses and site-specific geophysical surveys. The procedure, tested with reference to the prototype case study of Costa del Canneto slope in Southern Italy, proves to be a useful tool to reduce the uncertainties associated with the presence of complex subsoil settings, including potential buried morphologies. Indeed, over several geotechnical models tested, the numerical analyses provide amplification profiles of the fundamental frequency reasonably comparable with data from ambient vibration measurements only for few of them. This allows to restrict the number of possible slope models and can be used to guide the design of additional in-situ geotechnical investigations needed to better characterise the stratigraphy of the area and constrain the geometry of the expected buried morphologies.