The Study Of Overtopping On Sloping Seawall Under Oblique And Multidirectional Irregular Waves

Sloping seawall and revetment is a familiar type of structure in coastal regions and the overtopping discharge on it is a key parameter to determine its crest height. In the former studies, mostly work is limited to investigate the overtopping for unidirectional waves with a normal incidence. However, multidirectional waves approaching with a oblique direction relative to structure is familiar in actual project circumstances. Meanwhile, main studies performed on overtopping discharge is limited within mean overtopping discharge until today, and rare have been done on the single wave overtopping which have a closely relation with the short time effects of overtopping. So to the end of improvement of project design level, performing a deep and systemic study into the problem of overtopping and especially the single wave overtopping under oblique and multidirectional wave is very necessary.Physical model test have been carried out in the multidirectional basin at the State Key Laboratory of Coastal and offshore Engineering, Dalian University of Technology. The JONSWAP spectrum suggested by Goda was used to simulate irregular waves, and the Guangyi-type distribution function was used to simulate the direction distribution of wave. Angle of incidence varied from 0°to 45°, and three distribution parameter, s=10, 40,∞were tested. The armor layout have two type: concrete armor and doloss armor, and the former has three slope ratio, 1.5, 2.0, 3.0, the latter has one, 1.5. In the test, a equipment developed by ourselves was used to measure the mean discharge, number of overtopping wave and single wave overtopping.After careful analysis to the data measured in test, the influences on wave overtopping of wave angle, direction distribution, slope ratio, relative freeboard height, armor type and so on were investigated. Two formulas used to calculate the mean wave overtopping discharge of oblique and multidirectional irregular waves on sloping seawall and the formulas used to calculate the exceedance probability and maximal value of single wave overtopping are presented.A numerical model based on nonlinear shallow water equations and finite volume method is developed, which can calculate the overtopping discharge of oblique and multidirectional wave on sloping seawall. Results come from the numerical model have a well fit with that measured in test, and can reflect correctly the pertinent variation trends. With the aim of studying closely the influence of wave direction angle and distribution on overtopping, a more careful investigation on them in a more wide extent by numerical model is carried out, and the results are presented.