Evaluation of passive pile analysis methods using three-dimensional finite element analysis

Piles in soft soil supporting bridge abutments are often exposed to passive loading induced by adjacent bridge approach embankment. Several methods for analysis of passive piles have been developed, but the international design specifications do not recommend a specific method for the analysis of passive piles. Therefore, the applicability of existing empirical and analytical analysis (conventional) methods is examined by comparing their outputs with those of a validated finite element model (FEM) at various adjacent embankment stress levels, and construction times, soft clay thicknesses, and pile spacing to diameter ratios. Outputs of both conventional methods and FEM show that increasing the embankment stress, thickness of soft clay layer, and pile spacing to diameter ratio results in an increase in the lateral pile displacement, maximum bending moment, and lateral pressure, and vice-versa on increasing embankment construction time. The outputs of the conventional analysis methods are compared to the FEM outputs and are underestimated except for few cases. The conventional analysis methods may yield better predictions at pile diameter-to-spacing ratio equals 3-4 for a soil preloaded prior to pile construction to a degree of consolidation greater than 50%.