Study On Longitudinal Vibration Of Cored Pipe Pile Under Groundwater Level Change

According to the fluctuation of groundwater level,the coupling dynamic characteristics of cored pipe pile and soil under longitudinal vibration load are studied.The vibration equation of soil layer and cored pipe pile under the influence of groundwater level fluctuation is established,and the dynamic equation is decoupled and solved in combination with boundary conditions.The theoretical solution of dynamic coupling between cored pipe pile and soil is obtained,and then compared with the numerical solution obtained by numerical simulation and the experimental solution obtained by indoor test,which further verifies the correctness of the theoretical solution.It mainly includes the following four aspects:(1)Study on vibration response of rigid supported pipe pile under groundwater level change.The soil around the pile is regarded as two-way heterogeneous soil and the pile bottom support is regarded as rigid support.Based on the complex stiffness transfer model,the coupling vibration models of viscoelastic soil,saturated soil and cored pipe pile are established respectively,and the dynamic equations are solved in combination with the boundary conditions.The changes of groundwater level,the properties of saturated soil,the comparison between soil plug and cored pipe pile are analyzed The influence of the change of core filling depth and the sediment thickness at the pile bottom on the dynamic response of the pile top.The research shows that the changes of soil properties and core filling depth have a significant impact on the longitudinal vibration characteristics of core filled pipe pile.(2)Study on vibration response of pipe pile supported by virtual soil pile under groundwater level change.Taking the soil at the pile end as a virtual soil pile,the vibration equations of soil layer and cored pipe pile under the influence of groundwater level fluctuation are established.Combined with the boundary conditions,the dynamic equations are decoupled and solved,and the time-domain semi analytical solutions and frequency-domain analytical solutions of longitudinal vibration of cored pipe pile under groundwater level fluctuation are obtained.After the pipe pile is reduced to solid core pile,it is compared with the existing theoretical solution of solid core pile.The effects of groundwater level change,core filling material,core filling height and the properties of virtual soil pile on the longitudinal vibration characteristics of core filled pipe pile are analyzed respectively.The research shows that the influence of the change of the properties of the core filling material and the change of the core filling height is obvious.(3)Numerical simulation of core filled pipe pile under groundwater level change.Through the finite element software ANSYS,the core filled pipe pile-soil coupling vibration models based on rigid support and virtual soil pile support considering the fluctuation of groundwater level are established respectively.The parameter changes under the two models are numerically simulated and compared with the corresponding theoretical solution curves,which verifies the correctness of the theoretical solution and the feasibility of the numerical fitting method.(4)Laboratory test of pile-soil model.Through the indoor pile foundation detection test of the core filled pipe pile model with different groundwater levels,the time-domain velocity curve of the pile top under different groundwater levels is obtained,and compared with the theoretical solution curve to verify the correctness of the theoretical solution and the experimental solution.