| Most coastal area of our country has marine or lacustrine soft deposits(i.e., with thickness ranging from several to dozens of meters) at the area of coast and seabed,such as the exit of Yangzi river, Zhujiang river and Bohai gulf. Because of poor physical properties of this soft clay, it has low bearing capacity. Investigation of dyke stability constructed on soft ground due to severe wave loading is extremely important.After construction hydraulic structures, dredging for waterway is generally required to improve the navigation conditions, maintain the channel size and to eliminate the flow pattern induced by ship navigation.In this thesis, limit equilibrium method was used to investigate dyke stability to determine the distance between channel dredging and heel of dyke. Moreover,numerical model of wave-dyke-ground foundation was built to analyze dyke stability under different conditions. By doing so, a reasonable range of channel dredging was proposed. In addition, centrifuge model tests were conducted to explore the stability of dyke due to excavation of muddy and to verify numerical results.Based on the limit equilibrium method, the influence of dredging on the stability of dyke was quite small. This is because sand at the outside of dyke was less and starting point of dredging was located outside the failure plane of the slope. It is demonstrated that the dyke stability was under control.According to the three-dimensional numerical analyses, dredging induced displacement in the dyke and ground was small. The horizontal movement was increased by 88 mm while much smaller vertical movement was observed. It is indicated that additional stress induced in the ground due to channel dredging and sediment deposition at the inner side of dyke was small.Based on the centrifuge test results, distribution of displacement vectors of dyke and underneath ground was even. Induced horizontal and vertical movements in the dyke and ground are in order of millimeter. It is indicated that channel dredging had small impact on the dyke. This is consistent with computed results from limit equilibrium and finite element methods. In general, computed movements from numerical analyses were slightly larger than those from centrifuge model tests. It implies that the constitutive model and model parameters adopted in this thesis were reasonable. |
