Numerical Simulation On Behavior Of Pile Foundations Under Lateral Cyclic Loading

The long-term cyclic wave action on pile foundation in marine environment will lead to the cyclic degradation of soil strength around the pile,and then affect the bearing capacity of pile foundation.Therefore,it is necessary to study the bearing characteristics of pile foundation under lateral cyclic load.At present,the p-y curve commonly used to analyze the pile-soil interaction has some limitations,such as the difficulty of parameter determination,unable to reflect the in-situ properties of soil.Moreover,the influence of cyclic loading type is not considered in the analysis of pile foundation response under lateral cyclic loading.Therefore,this paper focuses on the following aspects in view of the shortcomings of the existing research.Firstly,the p-y curve in clay is constructed based on the cyclic T-bar test.Based on the insitu cyclic T-bar test data,the mechanical parameters of soil strength,loading and unloading stiffness and strength degradation law are determined,and a monotonic p-y curve model without considering softening is established according to the numerical simulation and parameter analysis of pile plane strain model in deep soil.On this basis,considering the remolding and softening of the soil under lateral cyclic loading,a cyclic p-y curve model based on the in-situ cyclic T-bar test is developed,and its correctness is verified by comparing with the p-y curve data obtained from the simulation of lateral cyclic movement of pile foundation.Then,the degradation law of the behavior of pile foundations under lateral cyclic loading is studied by 3D finite element numerical simulation.Considering the effect of soil strength softening,ABAQUS/USDFLD is used to simulate the pile-soil interaction under lateral loading,and the degradation law of pile bearing capacity under different cyclic loading modes is studied.The results show that under monotonic loading,when the lateral displacement of pile top is 1D,the lateral bearing capacity,maximum bending moment and maximum shear force are reduced by 2.7%,2.5% and 1.2% respectively when considering soil strength softening,compared with the model without considering soil strength softening.Under constant amplitude cyclic loading,the larger the cyclic amplitude,the more significant the reduction of latera bearing capacity and bending moment bearing capacity.Under offset cyclic loading,the lateral bearing capacity and bending moment bearing capacity increase with the increase of offset,and the degradation degree and degradation rate of lateral bearing capacity increase significantly with the increase of cyclic amplitude,but also shows a trend of becoming larger with the increase of the offset.Under variable amplitude cyclic loading,the attenuation effect of large amplitude cyclic loading in the early stage on the bearing capacity of pile foundation in the subsequent small amplitude cyclic loading is very significant,while the attenuation effect of small amplitude cyclic loading in the early stage on the subsequent large amplitude cyclic loading is not obvious.