A study of transmission, reflection and stability of low-crested rubble mound breakwaters under wave action.

摘要

Two-dimensional physical models of low crested breakwaters were tested at the Queen's University Coastal Engineering Research Laboratory (QUCERL) to establish the effects of water depth, crest width, structure slope, stone size, core permeability and incident wave characteristics on the wave transmission and reflection processes. Effects of structure slope, core permeability, water depth and incident wave characteristics, (including wave groups) on the processes leading to damage were also studied. The breakwater models consisted of a core and two armour layers attacked by irregular waves.; Results of the experiments show the strong influence of water depth, crest width and wave period on wave transmission process. In the wave reflection process, results show the strong influence of water depth and wave period. The stability of low crested breakwaters was observed to be strongly influenced by the water depth and wave period.; Comparisons of the test results with the existing design equations do not seem to predict the wave transmission and reflection accurately for the range of the test data, especially for wide crest structures. Results of the irregular wave conditions required to initiate damage are compared to the design equations of Hudson and of van der Meer. The results and analysis presented herein support and are consistent with the design equation proposed by van der Meer. The equation takes into account the effects of wave height, wave period, structure slope, permeability and wave duration.; Alternative empirical models for the transmission and reflection coefficients were developed on the basis of dimensional analysis considerations and graphical inspection of the 2-D test results. The alternative models were evaluated on the basis of statistical measures and practical design considerations. The proposed relationships are useful in predicting wave transmission and reflection over a wide range of wave heights and covers variety of wave conditions and structural geometry. The models were verified with 3-D test results, showing that the proposed models predict the 3-D test data relatively well.; Given the complex nature of the processes at low crested breakwaters that cannot be clearly described using 2-D test data, a model has also been developed which describes the wave transmission characteristics based on a series of 3-D model tests. The 3-D model predicts relatively well K_t for both 2-D and 3-D test data.