MONITORAGGIO DI SITO E BACK-ANALYSIS NUMERICA DI UNA FRANA CLIMA-INDOTTA CON E SENZA L'EFFETTO DELLA VEGETAZIONE

The vegetation cover exerts a stabilizing action on slopes that can in many cases even prevent the development of landslides and, for this reason, it should always be preserved on natural slopes and embankments. Furthermore, the use of Nature Based solutions, e.g. engineering solutions based on natural processes, for landslide risk mitigation is rapidly spreading as a more environmental-friendly alternative to conventional grey solutions. Many and complex processes are involved in the soil-vegetation-atmosphere interactions, affecting both the hydraulic and mechanical behaviour of soils, but the conceptualization and quantification of their effects still result quite complex and inaccurate. In this work, real field data of a failure occurred in a Norwegian slope were accounted to investigate the interaction of the slope with the vegetation and the atmosphere. At first, numerical LEM and FEM back-analyses of the occurred event have been performed to corroborate the phenomenological reconstruction and obtain a reliable diagnosis. Afterward, the FEM model obtained has been used as a reference to investigate vegetated scenarios in which the root reinforcement has been modelled by accounting for a reinforced superficial layer by means of an additional root cohesion. A first 2D FEM sensitivity analysis has been performed to assess the minimum values of vegetation parameters needed to prevent the failure. Then, since the landslide occurred only in a portion of the slope where few months before the whole vegetation layer was removed, a 3D FEM analysis has been performed inducing a failure in a slope model only partially vegetated, that replicated the field condition.