Analysis of the stability of armour units during the 2004 Indian ocean and 2011 Tohoku Tsunami

The relative lack of frequency of major tsunami events has meant that little attention was paid in the past to the development of formulas to design breakwater armour against these events. However, field surveys of recent events such as the 2011 Great Eastern Japan Earthquake Tsunami and 2004 Indian Ocean Tsunami have shown flaws in the design of protection structures. In the present work, the authors have set out to improve the accuracy of the formula of Esteban et al. (2012) by expanding the analysis to a number of other ports that were affected by the 2011 Great Eastern Japan Earthquake Tsunami and the 2004 Indian Ocean Tsunami. The aim is to obtain a formula that can easily be applied by a practicing engineer to check whether a certain armour unit is likely to catastrophically fail during a given tsunami event. The improved formula proposed is based on that of Hudson but combining damage progression elements from the Van der Meer formula. The design of structures that only partially fail (i.e. "resilient" or "tenacious" structures) during an extreme level 2 tsunami event should be prioritized in future important protection works. Accordingly, the present paper makes recommendations on the acceptable level of damage for each tsunami level for various types of port installations.