Analysis and Verification of an Optimal Design Solution for Rubble Mound Breakwaters Considering Interactions of Failure Modes

Abstract

As an essential coastal structure, a breakwater is generally designed to be stable and reliable during its lifetime. With respect to stability, failure modes usually are statistically independent. However, the interaction of different failure modes can produce extra effects for the calculation of the total cost. Considering interactions of failure modes, this paper presents an analysis and verification of an optimal design solution for rubble mound breakwaters to minimize the total cost, including construction and repair costs. The three main failure modes, overtopping, armor instability, and crown wall sliding, are involved in the solution. An auxiliary coefficient representing the extent to which the failure mode (or interaction) affects the structure was used to calculate the extra repair cost along with the failure probability in the cost optimization. The aforementioned solution was applied to a real breakwater example, and a sensitivity analysis of the total cost of the design variables was carried out. The total expected cost using the optimal design solution was 19.1% less than the cost before optimization. Other coastal structures under wave impact loads can have the same failure modes and also could be optimized by the solution. The solution in this study can provide economical design recommendations.