Modelling the impact of landslides on geosyntethics-reinforced barrier using DEM-FDM analyses

Abstract

Geosynthetics-reinforced barriers can be used as protection structures for mitigating the risk posed by fast-moving flow-like landslides such as debris avalanches. In the design of such kind of barriers a crucial role is generally played by the correct analysis of the mutual interaction between the flowing mass and the barrier. This paper is focused on the evaluation of the impact forces and the deformation mechanisms of the barrier. An extensive numerical campaign of dynamic analyses has been performed by means of a coupled 3D Discrete Element Model (DEM) code, namely Particle Flow Code (PFC) and a continuum Finite Difference Method model, named Fast Lagrangian Analysis of Continua (FLAC3D code), both provided by Itasca software. The impacting flow with given initial height and velocity is here simply schematised as a dry granular mass, made of a random distribution of rigid spherical particles. The barrier is conceived as multilayered embankment reinforced by geogrids wrapped around the facing. The geometry of the barrier and the combinations of the materials have been varied to take in account a large variety of factors, also including the size of the impacting mass, the inter-particle friction angle and the initial velocity of the flowing mass. From the numerical results it was learned that the height of the flow may change significantly (or not) during the impact process depending on some of the previously mentioned factors. On the other hand, the global response of the deformable barrier depends on the combined behaviour of the granular soil and the geosynthetics reinforcements installed inside the barrier. Other novelty of the paper is that far from the semi-empirical formulations typically used for a safe design of such barriers, here the time-space dependent mutual interactions are accurately computed along the impact front also providing the chance to adequately take into account the mechanical features of the flowing mass and of the impacted barrier.