Prediction of the Settlement for the Vertically Loaded Pile Group Using 3D Finite Element Analyses

Abstract

The settlement prediction of small pile group at working load using 3D Finite Element (FE) approach was carried out based on the case of Belfast pile load test. Three different types of analysis were investigated: a linear elastic (LE) analysis where all the soil was assumed to be linear elastic, a complete nonlinear (CNL) analysis where both the soil adjacent to the pile shafts and between the piles using the Hardening Soil (HS) model, and a nonlinear and linear elastic analysis (NL-LE) with the soil close to the pile shafts using HS model while the soil in the remaining area is modeled as an elastic material. Then all the FE analyses were compared to the analytical approach (RATZ). The results of FE analysis suggest that incorporating a nonlinear zone of soil close the pile shaft and leaving the soil linear elastic beyond this zone gives more reasonable estimation of interaction factor, thus, a much better prediction of pile group settlement will be observed. It is suggested that a value of half the pile width for the distance from pile shaft to the edge of this nonlinear zone would be sufficient to capture the load transfer mechanism for a typical pile group. While best prediction was given by RATZ approach as the group settlement ratio which reflect the interaction effect between piles in the group obtained from RATZ mostly close to the field measurements.

Keywords:

• complete nonlinear analyses
• hardening soil model
• linear elastic analyses
• nonlinear elastic analyses
• pile group
• RATZ