Internal and external pressure measurements in reshaped breakwaters

Abstract

A series of hydraulic model tests was carried out to investigate the mechanisms by which reshaped breakwaters, that is breakwaters in which the initial profile is adjusted into a more stable profile as a result of wave action, gain their stability. This type of structure has been used frequently in the past decade, particularly in areas where a good supply of rock is available, and has been shown for these circumstances to have better stability characteristics and a much lower cost than conventional multi-layered designs. The breakwater models were instrumented with miniature stainless-steel diaphragm pressure transducers placed along the outer slope of the structure and along the core/filter interface. The motion of the phreatic surface within the internal porous matrix was determined using a set of specially designed capacitance gauges. A substantial reduction in the magnitude of the internal and external pressure fields was found for the reshaped structure compared with a conventional structure. The wave height at which the initiation of armour stone movement occurred was 60% higher for the reshaped structure than for a conventional breakwater armoured with two layers of the same size stone placed on a 1 : 2 slope.