The Distribution of Armour on Seawalls and Breakwaters: The Case for Tapered Surcharge

This paper discusses the non-uniform design of breakwater armour layers with the intention of properly examining the different load cases at different levels on a breakwater, so that consistent load factors are provided at each location. This concept has been called Tapered Surcharge. Early physical modelling and practical installations are compared with results from CFD analyses.

For over 100 years large rocks and concrete blocks have been used to provide an armour layer or carapace over smaller materials used for the structural core of rubble mound breakwaters. The design and deployment of such armour has developed both heuristically and experimentally. Conventionally, the armour layers provided are uniform in size from toe to crest. This paper examines non-uniform design considering the design flexibility of single layer arrays, based on simple theory and practical experiments and as exemplified by over 30 years worldwide experience with Seabees, and compares this with analyses of the underlying concept using modern numerical methods.