Discrete element analysis of settlement of pile groups

Abstract

Two discrete element models are described for the analysis of settlement of vertical pile groups. In both models, the piles are represented by discrete elements with an axial model of deformation, and the soil behaviour for the individual piles is represented by load-transfer curves. The essential difference between the models is the manner in which pile-soil-pile interaction is represented. The first model treats the soil as independent horizontal layers which permit interaction between piles to take place within the same layer only. Thus ignoring the continuity of the soil medium. The second utilizes Mindlin's solution which determines interaction effects in a homogeneous, isotropic elastic half-space, but an approximate procedure is used to account for soil inhomogeneity. Comparisons of both approaches with a rigorous integral equation method for pile groups in a homogeneous, isotropic elastic soil indicate that the second method generally gives good agreement while the first method tends to underestimate interaction, especially for shorter piles. For pile groups in nonhomogeneous soils, where rigorous theoretical solutions are generally not available, parametric studies comparing the two discrete element models solutions are presented. The studies performed using both methods on the nonlinear behaviour of an instrumented pile group compare favourably with the field measurements.