ROCK ARMOR DAMAGE IN DEPTH-LIMITED BREAKING WAVE CONDITIONS

Josep R Medina,M Esther Gã³Mez-Martã­N,Marã­A P Herrera

doi:10.9753/icce.v36.papers.21

Abstract

The armor layer of a mound breakwaters is usually designed with a formula derived from physical tests in non-breaking wave conditions; however, most rubble mound breakwaters are placed in the wave breaking zone where the highest waves break before reaching the structure. The hydraulic stability formulas developed for rock-armored breakwaters in non-breaking conditions are not completely valid to characterize the hydraulic stability of these structures under depth-limited wave attack. In this study, five series of 2D physical tests were carried out on a bottom slope m=1/50 to analyze the hydraulic stability of double-layer rock armored breakwaters in depth-limited breaking wave conditions. Measurements taken by 12 wave gauges placed along the wave flume were compared with estimations of Hm0, H2% and H1/10 obtained from numerical model SwanOne. The significant wave height, Hm0, estimated or measured at a distance 3hs from the toe of the structure was the best characteristic wave to relate armor damage with stability number. The six-power relationship between dimensionless armor damage and stability number, found in this study, explained more than 94% of the variance in the damage observations. This relationship is valid for conventional non-overtopping double-layer rock-armored breakwaters on bottom slope m=1/50 and depth-limited breaking wave conditions.

Highlights

The armor layer of a mound breakwater is usually designed with a formula derived from physical tests in non-breaking wave conditions; most rubble mound breakwaters are placed in the wave breaking zone where the highest waves break before reaching the structure.Since the pioneering work of Iribarren (1938), different formulas have been published to characterize the hydraulic stability of rock armors, such as those provided by Hudson (1959), Van der Meer (1988), Van Gent et al (2003) and other authors
ANALYSIS OF RESULTS Wave gauge measurements were taken without the structure and SwanOne software was used to estimate the depth-limited incident breaking waves based on incident waves estimated at the wave generation zone (G1 to G4) using the method developed by Figueres and Medina (2004)
Neither the Iribarren number nor hs were significant explanatory variables for the observed armor damage. Both water depth at the toe and wave steepness affect the stability of the armor layer, but the observations of this study indicate that this influence is well characterized by the significant wave height (Hm0) measured or estimated (SwanOne) in front of the structure

Summary

Introduction

The armor layer of a mound breakwater is usually designed with a formula derived from physical tests in non-breaking wave conditions; most rubble mound breakwaters are placed in the wave breaking zone where the highest waves break before reaching the structure.Since the pioneering work of Iribarren (1938), different formulas have been published to characterize the hydraulic stability of rock armors, such as those provided by Hudson (1959), Van der Meer (1988), Van Gent et al (2003) and other authors. Van der Meer (1988) analyzed more than three hundred experimental tests to propose his wellknown 10-parameter and 4-variable formula (see Eq 2) to estimate the armor damage in a conventional rubble mound breakwater as function of the stability number.

Results

Conclusion