| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系 === 89 === The influence of parapet position and movable seabed on run-up and overtopping for a seawall is preliminarily studied in the thesis, through the irregular wave experiments in a sand bed flume.
Referring to the section profile of southwestern coast and seawalls, the layout in the flume is made with a model scale of 1/15; the sand bed in slope of 1:30 nearshore and 1:80 offshore, a seawall with a slope of 1:1.5 and crest width of 26.7cm, as well as two kinds water depths (13.3 cm , 21.3 cm) at the toe of seawall. While a sequent of irregular waves were generated with T1/3 =2.07, 2.58, 3.1 and 3.61sec, breaking wave height, wave height in front of the seawall, run-up along the seawall slope and overtopping over the crest were measured simultaneously for dimensionless analysis.
The results reveal that the most 2% larger run-up R2% shows a good relation with the surf parameterξ, and overtopping parameter presents a positively correlation with run-up over the crest parameter(R2%/hc-1) in which q=overtopping quantity per unit width, Hs=significant wave height and hc=freeboard of seawall crest. As to the effect of the parapet position, it is found that the parapet on the backward of crest reduced run-up a little, but the overtopping may be reduced obviously to 10%~50% inversely with hc/Hs. On the other hand, the computed values of run-up and overtopping by Kobayashi (1983), Van der Meer (1992) and Franco(1999) formula for solid seabed were found to over-estimate those experimental values for the sand bed.
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