A Study on the Influence Boundaries of Stress Distribution in Physical Model Testing Boxes for Pile Foundations in Clay Soil Using 3D Finite Element Methods

Abstract

The influence boundaries of stress distribution in a physical model testing box for simulating pile foundations in clay soil were analyzed in this study. The data obtained was used to determine the appropriate dimensions of the testing box. Numerical simulations were conducted using three-dimensional finite element methods, with the clay soil behavior modeled using the Mohr-Coulomb model. The study was divided into four cases: a single pile, a raft foundation, and piled raft foundations with pile spacing-to-diameter ratios (s/D) of 2.5 and 3. The displacement boundaries of the soil surrounding the foundation under loading conditions up to failure were identified. The horizontal and vertical influence zones were determined as follows: for a single pile, 9.5D_pile horizontally and 9D_pile vertically at the pile tip; for a raft foundation, 1.1D_raft horizontally and 2.8D_raft vertically; for piled raft foundation with s/D = 2.5, 1.3D_raft horizontally and 22D_pile vertically at the pile tip; and for piled raft foundation with s/D = 3, 1.1D_raft horizontally and 19D_pile vertically at the pile tip. It was found that the physical model testing box must have dimensions at least five times the influence zones to minimize boundary effects. The findings provide a guideline for designing physical model testing boxes and can also be applied to define the numerical analysis boundaries for piled raft foundations in clay soil.