The purpose of this study is to perform an analysis of the structure stability of a breakwater concerning the effect of wave overtopping. First, a COBRAS model of Taichung Harbor breakwater structure is created. Secondly, the model is verified with experimental data, and reasonable agreement is shown between the two. Finally, the breakwater stability analysis under 50 to 250-year-return-period typhoon wave conditions as well as extreme wave conditions is discussed. The result shows that the failure of sliding is more dangerous than the failure of overturning in Taichung harbor breakwater. Under the extreme wave more than 100 year-return-period, the breakwater is unstable in sliding, whereas that is safe in overturning. The influence of Wave Overtopping on the Stability Analysis is dominated by the force on rear side of caisson and the phase difference on the two ends of caisson. If the impulse force happens at the moment of the minimum of the front force, the safety factor might decrease significantly and the failure of sliding might cause breakwater damage.


Wave-structures interaction is a typical occurrence in engineering practice for either coastal protection or harbor structure design. Many previous wave-structure interaction studies had discussed the effect of wave overtopping but some of which in structure stability analysis assumed seaward loads were static. Therefore, it is necessary to investigate the influence of wave overtopping induced seaward loads on structure stability.

In theory, there are some idealized theoretical models which had been presented (e.g., Sollitt and Cross 1972; Vidal et al. 1988; Liu and Wen 1997). However, all of analytical approaches became more complicated and inconvenient due to complex geometric practical problem. In different laboratories, hydraulic physical models had been used to study the problem (e.g., Allsop et al. 1985; Owen 1980; Franco et al. 1994; Van der Meer and Janssen 1995; Pedersen 1996; Hedges and Reis 1998; Franco 1999; Besley 1999). Nevertheless, it may be hard for the hydraulic physical model studies to overcome either scaling problem or high-cost.

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