Extended soil-arching analysis for piled embankments with rectangular pile layouts

Soil arching governs the performance of unreinforced piled embankments, yet studies largely focus on square grids, leaving rectangular layouts underexplored. This study derives analytical soil-arching solutions for rectangular pile arrangements by extending the Hewlett and Randolph soil-arching model and quantifies the error introduced by the common equivalent-square simplification. Centrifuge tests provide validation of the proposed model’s underlying load-transfer mechanisms under simplified conditions; subsequently, finite-element simulations extend the validation to broader parametric ranges and real fill properties, confirming the model’s applicability across various configurations. Parametric analyses show that the pile load-sharing ratio is governed primarily by the internal friction angle of the embankment fill. Increasing the pile-cap size moderately enhances arching-induced load transfer, whereas the shape factor has an overall negative effect. A higher friction angle of the embankment fill enhances soil arching at moderate embankment heights, but its beneficial effect diminishes beyond a critical height. This indicates that the stability of soil arching in high embankments can be improved by using fills with adequate frictional resistance and cohesive strength. For sand fills, an idealised arch is difficult to sustain, and prediction errors increase with embankment height; therefore, complementary numerical simulations are recommended for robust assessment.