Influence Of Pile Driving By High Frequency Hammer On The Surroundings In Soft Clay Using The Finite Element Method

As the technique of high frequency hydraulic vibratory pile driving has many advantages such as low vibration sense, low noise, light weight,high mobility etc., it is widely used in the domestic and foreign actual projects.However, Pile driving leads to significant changes in the main state variables of the surrounding soil and the penetration process may have an influence on adjacent structures such as pile foundation and reinforced concrete frame structures.The influence of pile driving by high frequency hammer on the surroundings has always been an important subject.In this paper, three-dimensional numerical analyses by ABAQUS are used to investigate the effects of pile driving on the surrounding soils and on the adjacent structures. The constitutive model of Mohr-Coulomb is adopted for the soft clay in the analysis.Pore pressure effects have not been taken into account,so the undrained shear strength parameters are used in this analysis.An explicit time integration scheme is used to simulate the dynamic installation. Near and far field of subsoil are modelled with continuum elements (C3D8R) and infinite elements (CIN3D8)respectively.A special technique to permit the penetration of the pile into the soil is shown:along the axis of penetration a rigid tube of 1.0 mm radius is modelled. At the beginning of the analysis this tube is in frictionless contact with the surrounding soil. During pile penetration the pile slides over the tube and the soil separates from the tube so that contact between the penetrating pile and the surrounding soil can be established.The parameters of high frequency vibration hammer reference ICE815C vibration hammer and the frequency assumes 25Hz.The mechanisms of high frequency hydraulic vibratory pile driving are elaborated, and the past research work are summarized including experimental studies, theorial studies and numerial analyse, meanwhile the basic theories of the finite element program ABAQUS on pile driving analysis are introduced.The whole process of high frequency hydraulic vibratory pile driving is modelled by finite element method, the changes of soil behaviour during the process including stress,displacement, acceleration, velocity are analyzed, conclude the law of the soil properties changes with the different penetration depth.The effect factors such as vibratory frequency,static loads, exciting force,the diameter of pile,the modulus of soil ect.on penetration speed and depth are revealed. At the pile toe show high lateral stresses and vertical stress due to stress interlocking.It also show the maximum positive and negative shear stress respectively at the pile toe on both sides.The pile driving beside the pile foundation or concrete frame structure are simulated.The changes of the driven pile and concrete frame structures behaviour during the process including internal force,displacement, acceleration, velocity are analyzed. The effect factors such as vibratory frequency,static loads, exciting force,the diameter of pile,the modulus of soil ect.on the driven pile internal force are revealed. Conclude the law of the internal force changes with the different penetration depth.