Kinematic response of floating piles in a saturated soil layer subjected to seismic S-wave propagation

Abstract

A mathematical formulation for the seismic analysis of floating piles embedded in a saturated soil layer to vertically propagating S waves is presented in this paper. Pivotal to the formulation is the establishment of a closed-form expression for the lateral soil reaction to pile displacement, and results from expressions for the free-field and scattered soil displacements obtained from Biot’s governing equations. Subsequently the pile is analysed as Euler-Bernoulli beam and the soil column between the pile tip and the bedrock is analysed as one-dimensional shear beam. This results in expressions for the kinematic response factors, that provide the frequency-dependent pile head displacement and rotation as function of the free-field soil movement. Validation of the developed model is followed by a discussion on the sensitivity of pile response to the two-phase nature of soil, focused on informing researchers and practitioners on the uncertainties introduced in conventional seismic analysis, where the foundation soil is modelled as single-phase medium.