A new non-axisymmetric 3D model of the pile-soil system for dynamic analysis of large-diameter piles under eccentric excitation load

Abstract

With the widely application of large-diameter piles for strengthening soft soil and supporting the offshore structures, the three-dimensional (3D) effect of large-diameter piles have been realized. However, most of the existing 3D theoretical models are axisymmetric, which consider the vertical and radical propagation of stress waves in the pile body during the low-strain pile integrity test (LSPIT). But it is difficult to place the excitation hammer accurately at the center point of the large-diameter pile top in the LSPIT, thus, the hammer-pile-soil system is usually non-axisymmetric. In this paper, a new non-axisymmetric 3D theoretical model is proposed to evaluate the dynamic characteristics of the large-diameter pile-soil system under eccentric excitation load, in which the pile and soil are simulated by the 3D continuum model. The rationality of the new non-axisymmetric solution is verified by comparing it with the results calculated by the finite element model (FEM) and the results derived from the existing 3D theoretical models. Finally, the optimal relative positions of the impact point and the test point in the LSPIT are acquired to weaken the high-frequency interference of the large-diameter pile top. The conclusions drawn from this study provide some useful guidance for evaluating the results of LSPIT.