Finite-element modelling of axial capacity of tapered steel piles in coarse-grained soil

Finite-element (FE) studies of tapered steel jacking piles with different diameters, installed in saturated and dry sands with various relative densities, were carried out and subsequently validated against full-scale experimental results. The purpose of this paper is to find an optimal way of numerically modelling tapered displacement piles installed in dry and saturated soil conditions and adopt the empirical relationships for predicting the bearing capacity components of this type of displacement pile incorporating the installation effects, whereby the bearing capacity factor, $Nq$⁠, and coefficient of lateral earth pressure, $K$⁠, were back-calculated. In numerical simulations, three-stage models are developed using two constitutive soil models: the HS-small model (hardening soil model with small-strain stiffness) and the UBC3D-PLM model. In addition, to improve the accuracy of the FE results, soil–soil interface elements are introduced based on the previously identified failure mechanisms from wished-in-place FE analysis.