TXT-tool 3.385-1.2: Deterministic Landslide Susceptibility Analyses Using LS-Rapid Software

Abstract

This paper presents the landslide susceptibility analyses on flysch slopes in Istra, Croatia, performed using deterministic three dimensional analyses in LS-Rapid software. The area of investigation is in the Pazin Paleogene Flysch Basin in the northeastern part of the Istrian Peninsula. Using deterministic approach in landslide hazard and risk analysis includes gathering of fundamental data about geometry, soil strength parameters, cover thickness and groundwater level, as well as the application of numerical models in safety factor calculation. LS-Rapid uses 3D models for simulation of progressive failure phenomena, developed to assess the sliding initiation and activation of landslides triggered by earthquake, rainfall or their combination. Detail distribution of pore pressures or the groundwater level inside the slope is taken into account trough the pore pressure ratio r_u, which gradually increases until the failure appears in a certain part of the slope. If this approach is applied on the wider area, in which it is possible to define the relative position of the sliding surface, it is possible to obtain the values of the critical pore pressure ratio that causes conditions in which failures occur in specific parts of the investigation area. Connecting the critical pore pressure ratio with distribution of rainfall it is possible to obtain the landslide susceptibility and landslide hazard. The model was validated through the interpretation of stereopairs and engineering geological mapping, and the results have shown that landslides inside the zones in the model that were characterized as highly susceptible, occurred in the nearest of farthest past.