The influence of toe geometry on toe armour stability for conventional rubble mound breakwaters

Rubble mound breakwaters have toe structures that support the armour layer and prevent scouring damage, making toe failure a primary failure mode. Existing formulae for toe stability yield conflicting results, often neglecting factors like storm duration and armour layer slope. This study tested a statically stable rubble mound with a rock-armoured toe under irregular waves. The effects of wave height, wave period, armour layer slope and water height on toe stability were investigated. Toe width had no effect, while relative depth was a key factor. Increased wave height and storm duration led to greater toe damage. The results emphasise the need for a new stability number, considering wave breaker type and armour layer slope, with a critical Iribarren value of 4.1. Based on this study and the findings of another study, new formulae for estimating toe damage were developed and validated using data from other studies.