Pile Foundation Dynamic Load Model Test And Numerical Simulation Study

In today’s engineering construction,whether it is the erection of bridges,excavation of foundation pits or the development of underground space,the use of pile foundations is indispensable,including bridge pile foundations,support piles or building pile foundations.At the same time,the soil material properties are variable and complex,so it is important to study the settlement and bearing characteristics of pile foundation under dynamic load.This paper relies on the National Natural Science Foundation of China project,using theoretical analysis,experimental research and numerical simulation methods with different modeling strategies to study the settlement law and bearing characteristics of pile foundation under dynamic and static loading,the main research content is as follows:(1)From the theoretical research related to pile bearing and pile-soil contact surface,the basic theory of pile-soil load transfer and monopile bearing capacity is analyzed,including the basic equation of pile top load transfer,the mechanism and law of pile-side pile end resistance transfer,pile-soil contact surface unit and principal structure model,pile top load effect and vertical bearing capacity calculation specification,so as to lay the foundation for subsequent research.(2)Through the basic physical mechanics tests,the basic parameters such as water content,density,cohesion c and internal friction angle φ of the studied soil samples were obtained;through the indoor direct shear tests of the soil itself and the pile-soil contact surface,the shear characteristics of the pile-soil contact surface under different normal pressure and roughness conditions were analyzed,and the shear characteristics of the soil itself were compared with the shear characteristics at the contact surface.(3)Dynamic load tests on model piles were conducted.The influencing factors studied include the number of load cycles,pile length,dynamic and static load ratio and load frequency,and the dynamic indexes studied include pile top settlement,pile top dynamic displacement amplitude,pile top acceleration,earth pressure and pile shaft force.The settlement pattern and dynamic indexes of pile foundation under dynamic load are summarized through experimental research.(4)A numerical simulation study of model piles was carried out using a mesh modeling approach.With the help of FLAC3 D software,the pile foundations and soil were modeled and the dynamic calculation was performed to further investigate the degree of influence of load parameters on the dynamic response of the pile foundations.At the same time,the influence of soil deformation modulus,soil cohesion and soil internal friction angle on the settlement and bearing of pile foundation were studied.(5)A numerical simulation study was conducted using a coupled finite difference-discrete element method.Based on PFC2 D granular flow software,the contact surface shear was simulated,and both monopile-double pile and triple pile models were established to study the vertical displacement,load bearing characteristics and force chain distribution.