Performance of Railway Embankments on Soft Ground Improved with Partially Encased Granular Columns

Studies on the effectiveness of partial encasement of granular columns in improving the performance of railway embankments on layered soft ground are limited. To address this gap, a finite element analysis (FEA) was performed using an axisymmetric unit cell model to evaluate the influence of a single granular column on the surrounding soft soil. A fully coupled flow-deformation analysis was adopted to capture both consolidation and irrecoverable settlements, as well as temporal changes in excess pore water pressure during the construction phase of an embankment. Partial encasement lengths of 20%, 40%, 60%, and 80% were analysed and compared with ordinary and fully encased columns under staged construction and train loading conditions. After the sequential embankment construction, equivalent dynamic train loads of 25 and 35 tonnes have been applied at speeds ranging from 40 to 160 km/h to evaluate the response of the improved soft ground. Further, a moving load analysis was conducted using the axle load and geometric specifications of the Alfa Pendular train to assess the undrained response of the improved soft ground. Embankment settlement and stresses were predicted at the base of the embankment, including at the top of the granular column and surrounding soft soil, and the results are presented. These outcomes provide valuable insights for practitioners, enabling informed decision-making for the design of embankments with partially encased granular columns in soft ground.