Dynamic impedance of a pipe pile in layered soils under vertical excitations

This paper investigates the dynamic impedance of a vertically loaded pipe pile embedded in layered soils. The dynamic response of pipe piles is governed by the 1D vibration theory, which is formulated as a series of matrix equations. Meanwhile, the dynamic solution for layered soils is achieved by the application of the stiffness matrix deduced from the analytical layer-element method. Based on the displacement compatibility and traction equilibrium at the interface between the pipe pile and both inner and outer soils, the dynamic pipe pile-soil interaction equations are established and solved efficiently. The validity and accuracy of the proposed method are demonstrated by the solutions of vertical impedances of a solid pile and a pipe pile embedded in a homogeneous half-space. Some numerical results are presented to explore the effects of wall thickness, length-radius ratio and layering of soils on the vertical impedances of pipe piles.