Performance of Passive Loaded Pile Group in Multilayer Subsoil

Abstract

In this study, numerical analyses were conducted to investigate the behavior of passive loaded pile group in multi-layer subsoil. Three-dimensional finite element code Plaxis 3D 2020 was used in the back analyses of centrifuge tests carried by Ellis (1997). Two different approaches (Approach 1&2) for simulating structural elements were applied in the numerical models. In Approach 1, piles, pile cap and abutment wall are simulated using volume elements, while in Approach 2, piles are simulated using embedded beam element and abutment wall and pile cap are simulated using plate element. Two different constitutive models (SS&SSC) were used to simulate the soft clay layer to choose the appropriate model in modeling the passive loaded pile groups. Lateral movement of soft clay layer, lateral displacement of rear pile and bending moment of front and rear piles were calculated in different conducted numerical models just after the embankment construction and at 90% degree of consolidation to be compared with measurements of centrifuge test. The calculations of the numerical models were extended to the end of design life of structure to study the effect of secondary consolidation settlement (Creep) on performance of the piles. A comparison between results obtained from the numerical models and existing empirical and analytical approaches was presented. Additionally, the effect of several parameters such as embankment load, thickness of soft clay layer, ratio between pile spacing and diameter and time of construction of embankment has been investigated in numerical models, empirical methods, and analytical approaches. The results have demonstrated the importance of conducting real three-dimensional finite element analyses to model the complex soil-structure-interaction that governs the performance of the passive loaded piles.