Research On Stability Of Breakwater In Soft Soil Foundation Based On Large Scale Model Experiment And Numerical Calculation Method

The soft soil foundation is widely distributed in the coastal area of our country,and it is a practical problem to construct breakwater on soft soil foundation in port and coastal engineering.It is not clear that the stability and failure mode of breakwater under the wave cyclic loading from the example of failure on semi-circular breakwater in Yangtze Estuary Deepwater Channel Regulation Project,so the bearing mechanism of soft soil foundation needs to be revealed.It is great scientific significance and practical value to reveal the bearing mechanism and stability of breakwater on soft soil foundation under wave load based on the large scale physical model experiment simulating the real working state and dynamic finite element method calculating or analyzing.This paper mainly carried out five aspects of research work.1.The stability experimental study on the large scale physical model of the semi-circular breakwater and the vertical caisson breakwater on soft soil foundation under wave loads is carried out for the first time.The model soil is produced by soil remolding,and the ratio of the ultimate bearing capacity of the model to the prototype soil is in line with the requirements of the model test.The experimental flume of physical model has a length of 450 m,a width of 5 m,a depth of 8 ~ 12 m,and the breakwater model scale is 1:5.The physical model experimental system is established in this flume to simulate the actual working state of wave-breakwater-soft soil foundation,and the relevant experiment studies are also performed.2.The pore water pressure changes on soft soil foundation under the semi-circular and the vertical breakwater structure types are studied by the large scale physical model experiment method under different wave parameters such as wave height,cycle number and different water depth.The development trend of the maximum pore water pressure of soft soil foundation under semi-circular breakwater can be classified into four kinds: basic invariant type,growth type,dissipative type and dissipation-before-growth type,while that of the vertical caisson breakwater can be classified into two kinds: basic invariant type and growth type.From the growth curve of the structure safety unfavorable angle,the logarithmic and hyperbolic maximum pore water pressure development model of the soft soil foundation under the semi-circular breakwater and the vertical breakwater are obtained,which lays the foundation for the cyclic strength weakening simulation of soft soil.3.According to the large scale physical model experiment,the soil strength of soft soil and the settlement characteristics of breakwater under the long-term action of wave loads are studied.And the different change rules of soil strength and settlement characteristics of semi-circular and vertical caisson breakwater are obtained,which provides a basis for the analysis of foundation soil bearing capacity and settlement under different structure types of breakwater.4.The finite element mathematical model of semi-circular breakwater and vertical caisson breakwater considering the weakening effect of soft soil foundation is established,which is verified by the large scale physical model experiment.With consideration of the influence of the wave dynamic load amplitude,the static load of the foundation bed,the type of the breakwater structure and the width of the foundation on the bearing capacity and strength weakening of the soft clay foundation,the method of determining the bearing capacity of the foundation considering the softening effect of soft soil foundation is established,which can be used in the stability calculation and analysis of the breakwater and provide technical support for the construction.5.Based on the finite element analysis method and the discrimination method of foundation bearing capacity of the soft soil foundation,the structural stability of the semi-circular breakwater in Yangtze River estuary deepwater channel regulation project and the vertical caisson breakwater in the west port of Yantai Port are analyzed.It provides the case support for the experimental method of the large-scale physical model,the numerical calculation analysis method and the discrimination method of foundation bearing capacity proposed in this paper.