Numerical Modelling of Inclined Piles in Settling Soil

Abstract

The allowable load for slender end-bearing piles in soft soils driven or drilled to compact till or rock frequently depends on the structural capacity of the pile. Pile groups consisting of such slender preceast concrete or steel piles often include inclined piles, since such small-diameter piles have a limited horizontal bearing capacity. Inclined piles placed in settling soil are subjected to a lateral force, which reduces the pile structural capacity. The simplified beam-spring design methods normally used to predict the impact on the structural capacity of inclined piles in settling soil are currently very crude because of the simplified description of the real pile and soil. On the other hand, the possibility to accurately calculate settlements in soft soil is highly developed, and it is possible to include creep effects in routine settlement calculations. There is currently no direct link between the advanced settlement analysis and the crude beam-spring idealization of inclined piles in settling soil. A full numerical model containing both the pile soilstructure interaction and the settlement process is very time-consuming to run and associated with mesh convergence and contact formulation problems. Herein a suitable modelling idealization of the settling soil is discussed, in which a settlement distribution from an advanced FEM-analysis is adapted to a simplified FEM or beam spring analysis suitable for practical design. The calculation method is compared to field measurements, and is shown to compare well with the field case. A strategy to adapt the settlement profile to model calculation of inclined piles is discussed.