Pressures on a rubble-mound breakwater crown-wall for tsunami impact

Abstract

Rubble mound-breakwaters are commonly constructed with a parapet or crown-wall at the crest. The design of these superstructures depends on the expected storm wave load history throughout the service life cycle. In tsunami-prone areas, this design must include tsunami actions since their loads can definitely exceed those of storm waves. However, tsunami loads are rarely accounted for. This study aimed at incorporating tsunami actions in the design of crown-walls of rubble-mound breakwaters for the first time. Within this scope, laboratory experiments on a scaled model of a typical Mediterranean rubble-mound breakwater typology under tsunami actions were conducted. This paper is the continuation of our previous paper, Aniel-Quiroga et al. (2018) [1], in which experiments were presented and a stability analysis of the armor units was conducted. This research paper presents the second part of the analysis focused on understanding the pressures that crown-walls of rubble-mound breakwaters must support due to tsunami-like actions. These pressures were measured and analyzed, providing the horizontal and uplift pressure time series and laws. The magnitude and timing of the maximum pressure peaks were identified. The maximum horizontal pressure is caused by the first impact of the tsunami. By contrast, the maximum uplift pressure is prompted by a pressure wave generated by the overtopped water falling into the leeside. This pressure wave penetrates the structure from the rear slope. As a result of this analysis, pressures were characterized, allowing the presentation of a new complete methodology that provides, for the tested structure, the design procedure of the crown-wall under tsunami actions. A new formulation to calculate the run-up of solitary waves on the tested rubble-mound breakwater slope is presented here.