Physical Model Investigations On Stability Of Breakwater Armor Under Stem Wave Action

Under a certain condition wherein the incident angle of wave is smaller than a critical angle, the wave is not reflected as a normal way, and there appears a wave propagation along the structure, called the Stem wave. The wave height and area of stem wave increases and the energy also concentrates as the wave travels along the structure. The stem wave will impact the edge or ledge part of structure, the wave force and current due to breaking wave will influence the stability of structure.The stability of armor unit is the major consideration during design. Ihe stability of breakwater structure is commonly verified by formula and physical model. In many design standards, Hudson's formula is adopted for calculating the size of armor unit. Hudson's formula was developed for armor unit by extensive hydraulic model tests in flume. But due to the limitation of model test, this formula can't describe the actual case in 3-dimension absolutely. During the stability model test, there are two types of models, one is 3D wave physical model in wave basin, and the other is 2D wave physical model in wave flume. The wave is only normally acting on structure for 2D model, while the 3D stability physical models are better for complex wave condition, such as breakwater head or joint part of breakwater.In this thesis, based on physical model test results of 2 projects, the stability of armor unit and instability reasons under stem waves is analyzed, and the improvement method is also presented. Based on the comparison among Hudson's formula, 2D physical model and 3D physical model, we can find that, under the complex wave condition, the 3D model is necessary for verification on stability of armor unit.