A theoretical analysis of vertical dynamic response of large-diameter pipe piles in layered soil

DING Xuan-ming(丁选明)^{1, 2}, ZHENG Chang-jie(郑长杰)², LIU Han-long(刘汉龙)^{1, 2}

(1. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,
Hohai University, Nanjing 210098, China;
2. College of Civil Engineering, Chongqing University, Chongqing 400045, China)

Abstract:Considering the viscous damping of the soil and soil-pile vertical coupled vibration, a computational model of large-diameter pipe pile in layered soil was established. The analytical solution in frequency domain was derived by Laplace transformation method. The responses in time domain were obtained by inverse Fourier transformation. The results of the analytical solution proposed agree well with the solutions in homogenous soil. The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched. The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil. The smaller the shear modulus, the larger the amplitude of velocity admittance. The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil. The displacements of the piles with the same damping coefficients of the outer soil have less difference. Moreover, the effects of the distribution of soil layers are analyzed. The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer. A larger damping coefficient of the upper layer results in a smaller velocity admittance. The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.

Key words:dynamic response; large-diameter pipe pile; layered soil; velocity admittance; dynamic stiffness