3D numerical modeling of a geosynthetic-reinforced pile-supported embankment – stress and displacement analysis

Piles or columns have been successfully used in combination with geosynthetics to support embankments over soft soil for several decades. The inclusion of geosynthetic reinforcement over piles is to enhance the load transfer from the embankment soil to the piles, reduce total and differential settlements, and increase slope stability. A constructed geosynthetic-reinforced pile-supported embankment to support railways over deep deposits of peat and soft organic soils in Berlin, Germany was selected for numerical modeling and analysis. Precast piles and caps and a load transfer platform consisting of three layers of geogrid reinforcement and granular materials were utilized in this project. A finite difference method, incorporated in the FLAC 3D software, was employed to model this embankment. In the numerical analysis, piles were modeled using pile elements and caps were model as an elastic material. Geogrid elements built in the software were used for representing the geogrid reinforcement. Embankment fill, soft soil, firm soil, and platform fill material were modeled as linearly elastic perfectly plastic materials with Mohr-Coulomb failure criteria. The effects of variations of soft soil modulus below the embankment on the vertical displacements, stresses above pile caps, bending moments on the piles, and tension in reinforcements were investigated. The computed settlements of the embankment and the tension in reinforcements were compared against the measured results.