Stability analysis of sea-cliffs coupling stress strain and hydrodynamic modelling as a tool for modern archeological site preservation strategies

Cultural heritage (CH) sites are frequently situated in coastal areas that experience landslide activity, potentially influenced by climatic effects. A growing number of studies have directed their attention toward investigating mitigation strategies for CH sites impacted by landslides. Nevertheless, there is a paucity of quantitative studies dedicated to elucidating the relationships between coastal landslide activity and climate-related factors. Specifically, the comprehensive understanding of the extent to which both preparatory and triggering climate-related factors contribute to slope instabilities remains incomplete. This knowledge gap is particularly pronounced in the case of waves and wind, whose impact is extensively examined in coastal engineering applications.
The Punta Eolo sea-cliff (Ventotene island, Italy) is here analyzed since it is frequently affected by rock-falls and topples that are threatening the vulnerable remnants of the roman archaeological site of Villa Giulia. This latter is one of the pilot sites selected in the framework of the H2020 TRIQUETRA European project, aimed to proposing a methodological framework for mitigating climate-related natural hazards affecting cultural heritage.
To account for the action of sea waves on a sea cliff, a preliminary attempt was made to couple hydrodynamic modeling of sea-related actions with stability analysis managed through limit-equilibrium and stress-strain approaches.  For the hydrodynamic modelling a mesh-based computational fluid dynamics (CFD) method, that had been validated previously for extreme wave impact on coastal structures both in 2D and 3D conditions, was utilized. The results of the hydrodynamic analysis (e.g., stress field applied on the cliff by waves impact) were then used as input data for the stability analysis. The slope stability conditions of Punta Eolo's sea cliff were evaluated for a rock-toppling mechanism; following that, slope stability analyses were carried out under static and pseudo-static conditions. The analysis considered both seismic action and static water pressure within the joint sets. In a subsequent phase of investigation, the sea-wave action was incorporated as a force accountable for an elastic rebound sensu Hutchinson (1988). Through hydrodynamic modeling, the maximum computed force exerted by sea waves against the cliff was converted into a pseudo-static coefficient. This latter served as input for the factor of safety (FOS) calculation.
The quantitative analysis has brought to light the potential occurrence of instability conditions in specific rock blocks when the hydrostatic backpressure resulting from the filling of rock cracks is coupled with a pseudo-static force, originating from the elastic rebound induced by the impact of sea waves. This scenario represents the most frequently encountered action at the examined cliff of Punta Eolo.
Finally, the project of the ongoing installation of a tailor-designed monitoring system in Punta Eolo is presented. This system aims to characterize the physical attributes of sea-related preparatory and triggering factors affecting the cliff, and to assess the deformative response of the cliff itself under the influence of periodic thermal and hydrodynamic stressors.