Abstract:ELASTOCOAST revetments are highly porous structures made of mineral aggregates (e.g. crushed stones) which are durably and elastically bonded by polyurethane (PU). Despite their numerous advantages as compared to conventional revetments and the large experience available from several pilot projects (e.g. in The Netherlands and Germany), physically-based design formulae to predict their hydraulic performance, wave loading and response are still lacking. Therefore, the present study aims at improving the understanding of the processes involved in the interaction between wave, revetment and foundation, based on large-scale model tests performed in the Coastal Research Centre (FZK), Hannover/Germany, and to provide formulae/diagrams for the prediction of (i) the hydraulic performance (wave reflection, wave run-up and rundown), (ii) the wave load on and beneath the revetment as well as in the subsoil for a wide range of wave conditions, including both impact and non-impact wave loads, (iii) the response of the revetment (flexural behaviour) and its foundation (pore pressure and effective stress). The failure of one of the three ELASTOCOAST revetment model alternatives A, B and C tested at prototype scale is also analysed on the basis of the data simultaneously recorded by more than 80 transducers synchronously connected to two video cameras. As a result, it is shown that the weakest ELASTOCOAST alternative failed due to transient liquefaction of the sand core beneath the revetment while another ELASTOCOAST alternative, synchronously tested under exactly the same wave conditions, did not fail. Generic implications are then drawn from these results for the design of bonded permeable revetments subject to water waves. Finally, a brief outlook is provided on the planned future research directed towards numerical modelling and the incorporation of these results in a design manual for polyurethane bonded aggregate (PBA) revetments. Keywords:Bonded permeable revetments -Wave impact loads -Wave-structure-subsoil interaction -Wave-induced pore pressure -Transient soil liquefaction 709Thème 5 -Ouvrages portuaires, côtiers et offshore 1. Introduction "ELASTOCOAST" has been introduced in 2004 for the shore protection of Hamburger Hallig as a new type of highly porous revetment made of mineral aggregates such as crushed stones which are durably and elastically bonded by polyurethane (PU). Since then ELASTOCOAST has been applied at 15 further coastal sites in Germany, four pilot sites in The Netherlands, four in France, two in the UK and one in Canada (see www.elastogran.de). As compared to their conventional counterparts, ELASTOCOAST revetments have many advantages. Wave run-up, and thus also the required height of the defence structure, can be substantially reduced as compared to smooth impermeable revetments. Moreover, wave reflection which may affect both navigation and sea bed stability is also reduced. The high porosity combined with the durable elastic bonding may result in a much smaller revetment thickness requir...

Polyurethane bonded aggregate (PBA) revetments are highly porous structures made of crushed stones durably and elastically bonded by polyurethane (PU). Despite their advantages compared with conventional revetments and the experience available from more than 25 pilot projects, design formulae to predict their hydraulic performance, wave loading and response are still lacking. Therefore, the paper addresses the analysis of large-scale tests performed in the Large Wave Flume (GWK) of Hanover/Germany. The study aims at improving the understanding of the processes involved in the interaction between wave, revetment and foundation and at developing the missing design formulae for a broad range of wave conditions. The analysis of an observed failure due to transient soil liquefaction under regular waves is also described.Les revêtements PBA (polyurethane bonded aggregate) sont des structures très poreuses composées d'agrégats liés durablement et élastiquement par du Polyurethane (PU). Malgré les avantages de ce type de revêtement et l'expérience de plus de 25 projets pilotes, il n'existe toujours pas des formules de dimensionnement pour le calcul de leur performance hydraulique, des efforts de houle ainsi que de leur réponse à ces efforts. C'est pourquoi cette étude est consacrée à l'analyse des essais à grande échelle dans le Grand Canal à Houle (GWK) de Hanovre/Allemagne. Ces essais visent à améliorer les connaissances relatives aux processus liés à l'interaction entre la houle, le revêtement et sa fondation et à développer les formules de dimensionnement pour une large gamme de conditions de houle. L'analyse d'un cas de rupture cause en houles régulières par une liquéfaction transiente est aussi inclue.

Elastomeric bonded permeable revetments, also called PBA (Polyurethane bonded aggregate) revetments, are highly porous structures made of mineral aggregates (e.g. crushed stones) which are durably and elastically bonded by polyurethane (PU). Despite their numerous advantages as compared to conventional revetments and the large experience available from more than 25 pilot projects, physically-based design formulae to predict their hydraulic performance, wave loading and response are still lacking. Therefore, the present study aims at improving the understanding of the processes involved in the interaction between wave, revetment and foundation, based on largescale model tests performed in the Coastal Research Centre (FZK), Hannover/Germany, and to provide prediction formulae/diagrams. This paper is focused on the prediction of the hydraulic performance (wave reflection, wave runup and run-down) and the response of the sand core (pore pressure) beneath the revetment for a wide range of wave conditions, including the analysis of an observed failure due to transient soil liquefaction.

Permeable revetments made of bonded mineral aggregates may increasingly be favoured compared to standard revetments. However, the physical processes associated with the water–structure–soil-interaction for a wide range of wave conditions are still not well understood. Therefore, systematic large-scale model tests have been performed in the Large Wave Flume (GWK) of the Coastal Research Centre (FZK) in Hannover, with the intention of improving the understanding of these processes.

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