An Analytical Method Evaluating the Evolution of Group Effect for Vertically Loaded Pile Groups Subjected to Tunnel Excavation

Abstract

Tunnel excavations near existing vertically loaded pile groups are frequently encountered in urban areas, and most available studies have focused on the additional deformation and stress induced in the pile group, lacking in consideration of the variation in the pile-soil interaction (PSI) in the process, which plays an important role in pile group behavior with close pile spacing. In addition, for vertically loaded pile groups subjected to excavations in their proximity, the combined actions of the overlapping stress and shielding effect can lead to complicated variations in the group effect, which in turn results in difficulty in evaluating the PSI relationship and the pile group response. Thus, the modified Poulos method is extended in this paper to account for the effects of tunneling, and the variations in the group effect, load redistributions and pile settlements are also investigated. The validity of the proposed method is firstly verified by an available centrifuge model test with tunneling near a 2 × 2 fixed-head pile group. Further, the influences of the pile spacing and relative distance between the pile group and the tunnel are analyzed, and the most unfavorable working condition could be a tunnel excavated near the soil surface, close to a pile group with a small pile spacing.