Studies On Theory And Behavior Of Lateral Vibration Of Pile Foundation

The horizontal dynamic behavior of pile foundation is becoming more and more attractive in geotechnical engineering. But the theory concerned with this is still in research stage. In this paper,the theory for lateral vibration of pile foundation with consideration of shear deformation of pile is established,and the influence of the ratio of pile length to its diameter,the ratio of pile stiffness to soil stiffness and dimensionless frequency were studied systemically.The Beam-on-Dynamic-Winkler-Foundation (BDWF) model was utilized to determine the lateral dynamic response of a pile with finite length in a viscoelastic soil. An analytical solution was obtained in the time domain for the vibration of a pile under a laterally cyclic force applied at the pile head. Based on the solution,the transient response of the pile loaded by semi-sine force was acquired with superposition principle. At the same time,the problem described above was solved in the frequency domain and the analytical solution for lateral steady response of single pile with finite length or with infinite length was developed under different boundary conditions.By using the solution developed and the frequency-dependent stiffness coefficient and damp coefficient,the dynamic behavior,especially the one concerned with the variation of the dimensionless maximum response along the depth,for the pile with finite length or with infinite length was studied. It was shown that to simplify computation a pile of finite length can be taken as the one of infinite length if the ratio of pile length to its diameter (i.e. lid) is greater than 15.A more rigorous analytical solution for lateral vibration of single pile in a homogeneous soil was developed,in which the shear deformation of pile was considered for the first time. Based on parameters studies,it was proposed that the critical value of lid is 8 beyond which the shear deformation can be ignored in common cases. Furthermore,the analytical solution for the lateral vibration of single pile embedded in layered soils was obtained,and the influence of the shear deformation on the lateral dynamic response was examined.On the basis of the developed solution for single pile considering shear deformation and the analysis method for two piles proposed by Makris (1992),the dynamic interaction factor between two piles was obtained and relevant parameter study made. The influence of shear deformation on the dynamic interaction factor was also studied. Accordingly,solution for the dynamic response of grouped piles taking consideration of shear deformation was developed by using superposition principle,and the effects of shear deformation and the other factors on the horizontal displacement and the distribution of shear forces at pile head were investigated.It is the work presented herein that for the first time gives analytical theories for the lateral vibration of single pile and grouped piles taking consideration of both bend deformation and shear deformation of pile. The shortcoming involved with the existed analytical theory which considered bend deformation of pile only is then overcomed. This makes the theory for lateral vibration of pile foundation more perfect.