Dynamic soil arching effect in pile-supported embankment due to train passages at high speeds

Abstract

Pile-supported embankment has been widely adopted for high-speed railways constructed over soft soils to reduce post-construction settlement. The role of soil arching effect in stress distribution inside pile-supported embankment under static weight load has been extensively studied, while the dynamic soil arching effect due to train moving loads has been paid little attention. In this paper, a sophisticated three-dimensional (3D) track-embankment-pile-subsoil finite element model (FEM) has been developed to analyze dynamic stress responses due to train passages at high speeds. The numerical model has been validated by experimental results on a full-scale pile-supported railway embankment model. The numerical analyses reveal that the dynamic soil stress distribution in the embankment near the track is almost consistent with the Boussinesq solution, but the presence of piles underneath the embankment leads to the redistribution of dynamic soil stresses inside the embankment due to the dynamic soil arching effect. The soil arch height under train load is 2 m (2.5 times of the clear space of piles), higher than the height 1.6 m (2 times of the clear space of piles) under embankment self-weight. Besides, the pile efficacy (ratio of load borne by the pile cap to the total applied load) caused by moving train load at 100 m/s is 0.6, which also is higher than the pile efficacy 0.57 caused by embankment weight. Train passage at high speeds significantly amplifies the dynamic stress intensity in the embankment but barely changes the pile efficacy.