Performance of Pile Group Affected by Adjacent Excavations in Sand below the Water Table

Abstract

Numerical analysis is conducted to investigate the settlement and tilting behavior of a group of piles adjacent to an excavation in saturated sand by using PLAXIS 3D finite element software. Moreover, the analysis aims to gain a better understanding of the load transfer mechanisms of the piled foundations due to an adjacent excavation. The influences of excavation depth, pile group location from excavation, initial working load, supporting system stiffness, and stiffness of piles and cap are investigated. As excavation proceeds, settlement and tilting of the adjacent buildings can be observed at different stages of excavation. The pile group settles to its maximum amount when the rear piles are in the position of maximum greenfield ground surface settlement. The settlement of the pile group can be significantly reduced by increasing the supporting system stiffness and decreasing the pile cap's applied load. The pile group settlement due to the excavation increases from 2.99 to 3.80% of the pile diameter when the ratio of applied load to ultimate load-carrying capacity of the pile group increases from 0.25 to 0.5. A clearly noticeable tilting can be observed when the pile group is located near the excavation. By increasing the pile cap's applied load and supporting system stiffness, the pile group tilting decreases. The settlement and tilting of the pile group are almost insensitive to the modulus of elasticity of the concrete piles and the cap. Loads are transferred between the toe and the shaft of the piles at different excavation stages.