Analysis and classification of stepwise failure of monolithic breakwaters

• Published in: Coastal engineering (Amsterdam) 2017-03, Vol.121, p.221-239
• Main Authors: Elsafti, H., Oumeraci, H.
• Format: Article
• Language: English
• Subjects: Breaking wave impact; Caisson breakwaters; Monolithic breakwaters; Residual pore pressure; Stepwise failure; Wave–structure–seabed interaction
• ISSN: 0378-3839; 1872-7379
• DOI: 10.1016/j.coastaleng.2017.01.001

Analysis, interpretation and classification of stepwise failure of monolithic breakwaters are presented. Through the stepwise failure mechanism, monolithic breakwaters develop incremental residual displacements with each wave load event. This mode of failure is associated with the highly complex processes involved in wave–structure–foundation interaction and may occur even under relatively moderate wave conditions. Based on the results of the analysis of a well validated CFD–CSD model system and large-scale physical model test data, a new concept, named load eccentricity concept, is proposed to classify the response of the foundation in four load eccentricity regimes. This concept is based on the relative eccentricity e/B, i.e. the ratio of eccentricity e of the vertical force resultant from the mid-point of the foundation–structure interface related to width B of this interface. In fact, the relative eccentricity carries all significant information related to the wave loads (horizontal and uplift forces) and to the properties of the structure (mass and geometry). Further, a new 3-DOF model, which can handle the system nonlinearity (e.g. soil plasticity), is developed for preliminary analysis. For the application of the model, only two parameters are needed: the relative load eccentricity and the relative soil density. •Stepwise failure mode of monolithic breakwaters is studied using results of numerical and large-scale physical modelling.•The relative load eccentricity and soil density are selected to describe wave-structure-seabed interaction.•The load eccentricity concept is proposed, by which the stepwise failure is classified into four regimes.•A new interpretation of stepwise failure and direction of breakwater tilt is presented.•Based on enhanced understanding, a simplified model for practical engineering use is developed.