An experimental study on the hydraulic stability of Icelandic-Type berm breakwaters

Abstract

One of the key aspects of breakwater design and safety assessment is their stability evaluation. In the present paper, hydraulic stability of a multi-layer berm breakwater (MLBB) has been studied through varying the parameter of eroded area. To this end, a 2-D experimental model has been carried out in the wave flume of Tarbiat Modares University using irregular waves with a JONSWAP spectrum. A total of 150 tests have been performed to cover a wide range of sea state conditions and geometrical parameters such as wave height, wave period, water depth, berm width, berm elevation, stone class I height, front slope and nominal diameter of stone class I. In this study, a new dimensionless parameter is introduced to indicate that the wave breaking type plays a fundamental role in stability of MLBBs. Eventually; a new formula is derived to estimate the damage of MLBBs, based on different sea state conditions and various geometrical parameters. Comparisons are made between the estimated damage parameter of MLBBs by the proposed formula and those estimated by existing formulae. The results denote that the present formula not only performs well for MLBBs experimental data, but also indicates a reliable performance for some of Lykke Andersen's (2006) data in statically homogenous berm breakwaters (HBBs) outside the range of given formula. Furthermore, an innovative approach is presented to examine the eroded area based on the berm recession and the intersection point of reshaped and initial profile from SWL, which performs faultlessly rather than the existing one.