Load transfer and performance evaluation of piled beam-supported embankments

A ground modification technique with rigid columns and ground beams for supporting an embankment over multilayered soft soils is introduced and investigated. A fully coupled three-dimensional finite element analysis was performed to examine the effect of beam inclusion into a piled embankment system. After validating the numerical model against field measurements, the time-dependent behavior of the innovative support system was further investigated with an isolated pile-supported embankment used as a control. A three-dimensional soil arch model is proposed for piles arranged in a square pattern with beam reinforcement. The kinematics of soil arching under staged construction of embankments and subsoil consolidation illustrates that the height of the outer boundary is generally lower with ground beams, suggesting that soil arching can be more easily mobilized in this configuration than in individual pile-supported embankments. When the tops of adjacent piles are connected with ground beams, load transfer to piles becomes more efficient, preventing the arch failure at the crown and punching shear failure at pile heads. Wider pile spacing leads to an increase in size and critical height of soil arches, while the fill over tops of beams may undergo larger plastic deformation. The inclusion of beams substantially reduces post-construction settlement and accelerates the dissipation of excess pore water pressure within soft soils. Performance of piled beam-supported embankment (PBSE) was ultimately evaluated by using two efficient comparison models. Under the same area replacement ratio conditions, PBSE significantly outperforms a geosynthetic-reinforced piled embankment with pile caps. Although PBSE is little less efficient than an embankment supported by slab–pile structure, the construction cost is substantially higher for the latter. A wider application of PBSE to high-speed rails is promising but it needs to be assessed against more field evidence.