Author(s): Dong-Hoon Yoo; Jong-Joo Yoon; Pyung-Kyo Jung
Linked Author(s):
Keywords: Breakwater; Armor weight; Iribarren number; Wave action slope; Local value of wave length
Abstract: The equation of Hudson is world-widely employed for the estimation of minimum or optimum weight of armor block. Various scientific engineers found that the optimum weight of armor block is also significantly influenced by wave period, percolation of slope, and the formation of irregular waves. The type of breaking waves is also one of the major factors for the determination of wave forces affecting beaches and coastal structures. Iribarren (1950) suggested a wave breaking parameter to determine the type of breaking waves and Iribarren number is in recent years widely employed for the estimation of run-up height and unit weight of armor block. Iribarren number is the ratio of beach slope to the square root of wave steepness. In this study new surf parameter, which is called‘wave action slope’, is introduced for representing the local wave conditions in shallow waters by employing local values of wave length as well as wave height. The use of linear wave theory on a flat bed of the depth at the front of breakwater might be considered far better than the simple adoption of the deep water wave length for characterizing surfing waves at a shoaling depth. The wave action slope is formed by the product of the breakwater slope and the celerity ratio to the wave height. The optimum or minimum weight of armor unit is related to the wave action slopes which are employed for developing new empirical equations. After analysing van der Meer (1988) laboratory data, we found the armor weights are well related to the wave action slope. Using the new surf parameter, simple but accurate equation can be suggested for the estimation of breakwater armor weight. Several empirical equations are applied to the cases of failure experienced in Korean East Coast. The values given by Hudson equation are found satisfactory for 26 cases of the total 57 failure cases. The number of satisfaction cases is found to decrease by using recent empirical equations, The equation of van der Meer-de Jong provides 17 among 57, the equation of van Gent 3 among 57, and the equation of Yoo 16 among 57. The decrease of satisfaction number might indicate some improvement of the new empirical equations over Hudson equation. But the equation of van Gent provides very excessive value of armor block weight in several cases.
Year: 2010