Study On The Load-bearing And Deformation Mechanism Of Rigid Pile-supported And Geosynthetic-reinforced Embankment

Geosynthetic-reinforced and pile-supported (GRPS) embankments are increasingly used to construct highways on soft soils due to their rapid construction, large treatment depth, and small lateral and post-construction deformation. However, the interactions among embankment fill, geosynthetic reinforcement, pile(cap) and foundation soil are complex, and the behaviors of GRPS embankments are still not well understood. To improve the understanding of this technology, the performance of GRPS embankments under static and dynamic loading conditions were investigated in this study through the combination of small scale model tests, theoretical analyses and numerical simulations. The main research contents are described as follows:A series of six group composite foundation plate loading tests with pure concrete piles having varied length-to-diameter ratios were performed, the settlement characteristics and load transfer mechanism were studied. In accordance with the observed behavior, a simplified method for calculating the stress concentration ratio of rigid pile composite foundation was proposed and validated against the test data.Based on previous research findings published in the literature, a simple and practical design procedure accounting for soil arching in the embankment fill, tensioned membrane effect of geosynthetic reinforcement and pile-soil interaction within the strengthened zone was put forward, and then the validity of this procedure was verified in comparison with field measurements.Parametric studies were undertaken to analyze the influence of embankment fill internal friction angle, embankment height, subgrade reaction coefficient and tensile stiffness of the geosynthetic on the performance of the GRPS embankment, which is characterized by pile load-sharing ratio, stress concentration ratio, tensile force and strain of the geosynthetic, subgrade stress reduction ratio and pile tip penetration.Two-dimensional(2D) elasto-plastic dynamic finite element models were established to investigate the deformation characteristics at the surface and toe of the GRPS embankments. The effect of various factors including embankment height, pile spacing, pile length, compression modulus of the pile and soft soil, tensile stiffness of the geosynthetic reinforcement as well as the frequency and amplitude of cyclic load were explored and discussed in detail.