Abstract: To explore the evolution law of the spatial arching effect of pile-supported low embankment, three kinds of three- dimensional movable gate particle flow models with different heights and low embankments were established by PFC3D software. Comparing the test results with the existing analytical solutions, the distribution characteristics of vertical earth pressure inside the embankment, the development mode of soil arches, and the settlement and deformation law of soil are analyzed. The results show that the spherical arch structure, which forms the path of load transfer, is composed of force chains at the top of piles after the pile-soil load sharing ratio reaches a steady state. The height of stress-arch increases first and then stabilizes as the filling height increases. Stable soil arching rate ? is in the range of about 0.2-0.4 at various positions on the trapdoor, which reflects the uneven earth pressure distribution. The vertical stress at the center of four piles is higher than that between two piles, and also larger than that at adjoining two-pile-centers. From the perspective of deformation, it can be judged that the height of equal settlement plane is about 1.2B times the net spacing of piles(B represents pile clear spacing) from the pile top, based on the contour of vertical displacement at different filling heights. The differential settlement, between particles above the pile top with larger settlements and particles above subsoil, grows with the increase of buried depth and presents an overall convex shape. As the settlement deepens, two different patterns of the external slip surface are observed according to surface deformation: triangular expansion pattern and equal settlement pattern. Particularly, the internal slip is dome-shaped under equal settlement plane.

Key words: piled embankment, soil arching effect, three-dimensional discrete element method, soil arching ratio, soil deformation