Experimental Study And Numerical Simulation On Cyclic Characteristics Of Soft Clay Under Complicated Combination Of Static Deviatoric Stress

Port construction in our country is in rapid development stage,larger ship and deeper water become the trend of the future,so it makes the port construction faced with severer marine and geological conditions.The previous study of circulating features of soft clay mainly concentrated in the two kinds of extreme situations of the static deviatoric stress fully consolidated or not.However,widespread soft clay in domestic coastal and offshore area will be weakened under cyclic loading.It may harm the stability of the port construction.Triaxial tests and numerical simulations on muddy-silty clay taken from Yantai littoral zone were finished,and the bearing capacity of soft clay foundations considering the weakening effect under cyclic loading was studied.The main contents are abstracted as follows:(1)Through the dynamic triaxial test and the laboratory's achievement,the accumulative pore pressure development subjected to the confining stress,drainage static deviatoric stress,undrained static deviatoric stress,dynamic stress and cycle times were studied.After the data fitting,the modified hyperbolic calculation models of the accumulative pore pressure was established.(2)Through the dynamic triaxial test,this paper analyzed the effective stress path of undrained shear law of development.Moreover,further exploration was done for the internal mechanism of strength changing with different confining pressure,drainage static deviatoric stress,undrained static deviatoric stress and dynamic stress.Finally,with strength weakening rule applied to the equivalent over-consolidation ratio formula,this paper established a cyclic strength changing model comprehensively considering confining pressure,drainage static deviatoric stress,undrained deviatoric stress,dynamic stress and cycles.(3)Based on the actual engineering,a finite element model of the caisson breakwater was established in ABAQUS.Integrating circulation strength changing model to the finite element dynamic calculation,a finite element model considering cyclic strength change law was established.(4)According to the actual project,the strength development in the soft clay foundation was studied considering the influenceof different horizontal wave loading,vertical wave loading,sand filling quantity in the breakwater and width of foundation,then the changing coefficient of subgrade bearing capacity calculation formula was put forward.In this way,we can provide a reference for practical engineering.