Three-Dimensional FEM Analysis of Bridge Pile Group Settlement in Soft Soils

Abstract

A numerical analysis is presented to simulate settlements of a pile group for a bridge on the Beijing-Tianjin Intercity Rail Passenger Dedicated Line in China. The pile group consists of eight cast-in-drilled-hole piles with a diameter of 1 m and an approximate length of 50 m. The finite element program Plaxis 3D was used in the analysis. The foundation soils were represented with the Mohr-Coulomb plasticity material model. The piles were represented with pile elements. Between the pile and the surrounding soil, interface elements were automatically generated by the program. In the analysis, the effects due to soil stiffness, pile length, and pile spacing were considered. The calculated results for the simulation of the pile installation sequence were compared with the measured results obtained from the field monitoring during and after construction. The settlements of the pile group under the anticipated super-structural loads were also calculated. Furthermore, allowable bearing capacity of the pile group was determined in the calculations and the safety factors for each calculation step was obtained. The results of the numerical analysis provide some insight to the settlement analysis of pile groups in soft clayey soils and the finite element program Plaxis 3D can be a useful tool for numerical analysis.