Finite element modelling types for rigid pile composite foundation under geosynthetic-reinforced embankment

Based on the in-situ test section of CFG pile composite foundation under geosynthetic-reinforced embankment, the finite element models for a single pile, group piles and full section are established, respectively, and the influences of the geometric model, pile-soil contact and other conditions on system deformation, stress distribution and load transfer are discussed. Mostly due to the influences of embankment boundary effect, the settlement and load distribution of the full-section model are both developed in time as the in-situ test results. The stress ratio (n) and the load-sharing efficiency of pile (E) both reach the maximum near the inner side of the embankment shoulder and are 15.7% and 5.2% higher than those in the center of the embankment, respectively. At the toe of the slope, the displacement vector angle of the pile top, the horizontal load and bending moment of the pile are quite significant. Under the surcharge with the same equal thickness, the single-pile model has similar performance with the group-pile model, and the settlement development of both is relatively slow and slightly lower than that of the full-section model. In each model, the predicted results show that n, E and the equal settlement surface height are all directly proportional to the differential settlement of soil-pile on the subsurface at the final computing time. The distribution of non-uniform vertical stress on the subsurface is shown according to the numerical results. According to the statistic results, the deviation between the test load and the theoretical load can be -35.1% to 58.5% within single-pile reinforced area. Setting the contact interaction to enable the relative displacement of pile and soil will increase both the settlement and the height of the equal settlement surface, and also affect the stress of the shallow pile shaft. The full-section finite element model with pile-soil interaction is recommended to investigate the composite foundation under reinforced embankment. © 2020, Editorial Office of Chinese Journal of Geotechnical Engineering. All right reserved.