Study On Interaction Between New Breakwater Structure And Soft Ground Foundation Under Wave Load

With the construction of breakwater into deep water area, the researches on interaction of wave-breakwater-foundation become more and more important. Bucket foundation breakwater is a new type of breakwater that is suitable for deep water area, large wave load and soft ground foundation conditions. The working mechanism of bucket foundation structure is different from common offshore structures such as gravity structure and sheet-pile structure, and the stability of this new structure is not only depend on earth pressure on foundation wall but also intensely depend on interaction between soil and structure. Taking the project of bucket foundation breakwater in Tianjin port as a background, the topic of interaction between complicated breakwater structure and soft ground foundation under wave load is studied through geotechnical centrifuge modeling technique, static and cyclic triaxial test and FEM simulation method in this dissertation, the main works carried out are as follow:(1) A static load which simulates the wave load is applied on breakwater in centrifuge test, and interaction between breakwater structure and soft ground foundation is studied, the displacement, stability of breakwater and pore pressure developed in foundation under static load are discussed, and undrained strength of foundation soil on work mechanism of the breakwater are also studied.(2) A new equipment which can apply non-contact cyclic load on structure in centrifuge test is developed, by using this equipment the interaction between breakwater structure and soft ground foundation under wave load is simulated, cyclic displacement, cyclic pore pressure response, displacement mode under different working conditions are analised, and the effect of wave load on undrained strength of foundation soil that adjacent to the breakwater is studied.(3) The effect of cyclic wave load on dynamic properties of soft clay is studied with cyclic triaxial test, a low frequency cyclic load is applied on the specimen, the effect of cyclic stress amplitude, consolidated stress and period on cyclic strain, cyclic pore pressure response and modulus degradation are studied. The development of accumulative axial strain, average pore pressure and degradation index are studied, the relationship between these index after cyclic load and influence of period on them are also discussed.(4) The effect of wave load on static behavior of soft clay is studied with post-cyclic static triaxial test, the influence of cyclic load on static effective stress path and pore pressure development are studied, static modulus degradation and influence of cyclic load on undrained strength are also discussed.(5) The interaction between breakwater and soft ground foundation is simulated through the ABAQUS finite element software, stress strain, displacement in foundation and earth pressure on foundation bucket are analyzed under different foundation height and overburden pressure conditions.