Review and analysis of vertical breakwater failures — lessons learned

Abstract

The failures experienced by vertical and composite breakwaters are briefly reviewed and the main reasons for failures are examined. The objective of this study is threefold: (a) identification of the weak components of the structure-foundation system, (b) illustration of the weak points of past and present design procedures and (c) development of a research strategy for the improvement of the technical basis for the design of vertical structures. First, three main categories of the reasons for failures are suggested: (a) reasons inherent to the structure itself, (b) reasons inherent to the prevailing hydraulic and loads conditions, and (c) reasons inherent to the foundation and seabed morphology. These reasons are then sytematically discussed and lessons are drawn which are related to each of the aspects considered. The results suggest that the present design approaches cannot explain most of the failure modes reported, and that the stability of vertical breakwaters is an integrated and complex problem which can satisfactorily be solved only by dynamic analysis and probabilistic design approaches.