Numerical Analysis of the Effect of Pile Tip Shape on Soil Behavior around Pile

Abstract

Underreamed (enlarged-base) piles are commonly employed in engineering practice. The pile tip is often made into different shapes. This study analyzes the effects of various underreamed pile tip shapes on the soil behavior around the pile. A finite element analysis combined with a mixed incremental method for the updated Lagrangian method is presented using a small strain formulation to solve the large deformation problem. Constitutive model for sand with particle crushing and joint elements are used to represent the behavior of sand around the pile and the interactive surface between the sand and the pile. The predicted relationship between the normalized bearing stress and displacement are compared with experimental measurements, showing good agreement. The numerical results demonstrate that the distributed area of the high-value radial stress contour and the high-value vertical stress decrease as the pile tip gets sharper. The distributed areas of the high positive-value vertical strain, the high negative-value radial strain and the high negative-value circumferential strain expand as the pile tip gets sharper. The numerical results clearly indicate that the soil beneath the pile tip at different depths displays various volumetric changes and confirms the necessity of the constitutive model for sand with particle crushing.