Soil stability analysis for wave-induced momentary liquefaction beneath porous bonded revetments

The highly porous revetments made of Polyurethane Bonded Aggregates (PBA) are an ecologically friendly alternative to conventional revetments for protection against coastal erosion. No information has yet been reported for these structures on failures from field applications. However, a well-documented collapse of a PBA-revetment observed in large-scale tests (GWK tests) and a first stability analysis were reported by Oumeraci et al, 2010; 2012. Based on these results, a methodology is proposed for stability analysis of the embankment subsoil beneath PBA-revetments against momentary liquefaction, considering the results of the comprehensive parametric study (Alcerreca-Huerta, 2014) using a recently developed CFD-CSD (Computational Fluids Dynamics Computational Solid Dynamics) model wavePoreGeoFoam (Alcerreca-Huerta and Oumeraci, 2016a; 2016b). It will be shown that the proposed stability analysis is able to reproduce the failure observed in the GWK tests, so that it can be applied for PBA-revetment under field conditions. In this paper, the failure observed in the GWK tests is first briefly reported, followed by a description of the numerical parametric study using the validated wavePoreGeoFoam model in order to extend the conditions tested in GWK. Then, the processes underlying soil liquefaction of PBA-revetments are outlined, showing that the excess pore pressure development in the sand core beneath PBA-revetments is crucial. The latter is therefore examined and a formula to predict excess pore pressures in terms of the wave conditions is developed. Moreover, a methodology for the stability analysis of the soil beneath the revetment against soil liquefaction is proposed and implemented to reproduce the failure observed in the GWK tests. Finally, the main results are summarized and implications for further research are drawn.