Analysis of Rubble Mound Breakwaters: Report of Working Group no. 12 of the Permanent Tecnical Committee 2 - Supplement to bulletin 78/79

Working Group 12 was set up to consider the analysis of rubble mound breakwaters with a view to achieving a better understanding of safety aspects. The working group decided to develop the practical application of risk analysis in the design of rubble mound breakwaters by using partial coefficients. Six subgroups, A-F, were established to carry out different aspects of the study. The reports of these subgroups are available in full at the General Secretariat of PIANC. The Main Report summarises the subgroup reports and presents the overall view of the results of the working group. A new system of design for rubble mound breakwaters has been developed whereby partial coefficients can be derived for any chosen probability of failure within the specified service life of the structures. Due to lack of general failure formulae, partial coefficients could only be determined for conventional multi-layer rubble mound breakwaters. The value of the new system has been demonstrated by examples based upon data collected by Subgroup E. A procedure is outlined for using partial coefficients to prepare and optimise preliminary designs. Hydraulic model testing should then be used to refine the preliminary design and provide the basis for the final design. The proposals included in this report should not be regarded as a recommended code for design. They may, however, be useful as guidelines for the development of a new and better way of improving safety of designs by using a more rational method of evaluating probabilities of failure during the life-time of a breakwater.