Modelling of geosynthetic-reinforced barriers under dynamic impact of debris avalanche

Abstract

This paper deals with geogrid-reinforced artificial barriers used as mitigation works against debris avalanches. Deformable Geosynthetic-Reinforced Barriers (DGRB) can be made of coarse-grained materials reinforced by high tenacity polyester (PET) geogrids, wrapped around the facing and arranged in layers. The peak dynamic impact pressure is here calculated as the sum of a landslide velocity-related component and a static component dependent on landslide height. Dynamic analyses are carried out through the commercial Finite Differences Method code (FLAC, Itasca) capable of adequately reproducing small and large displacements of the impacted barrier. The soil is modeled as elastic perfectly-plastic non-associative granular soil, the geogrids are simulated as traction-resistant, and the iron mesh framework is modeled as beam elements resistant to both traction and bending. Frictional interfaces are considered at soil-geosynthetic contacts. The displacements of specific control points and the global behaviour of the barriers are computed versus time. Tensile stresses in the geosynthetics are evaluated for different combinations of materials. Out of three geometries of the barrier, the more massive with the steeper impact front is outlined as the best choice. More deformable geosynthetics appear to be more effective in dissipating the impact energy inside the barrier.