Numerical Prediction of Tunneling Induced Surface Settlement of a Pile Group

Abstract

AbstractTunnel construction below or adjacent to the piles of Existing Building Structure (EBS) will affect the performance and eventually the stability of piles due to ground deformation which may result in the settlement of piles. A two-dimensional finite element analysis using PLAXIS 2D was performed to study the behavior of a pile group due to tunnel construction beneath the ground. A 15-noded plane strain model was used to simulate the soil structure. The Mohr–Coulomb (MC) model was used to simulate the soil–structure interaction at the tunnel–soil interface. An embedded beam row element was used to simulate the pile embedded in mixed soil conditions. An isotropic elastic plate element was used for modeling the existing building. A twin tunnel circular in shape was considered to be constructed underneath the building. Different tunnel locations are considered vertically and horizontally away from the building. A contraction volume loss of 0.5% during tunnel construction was adopted for analysis. The settlement of the building was found to decrease with an increase in tunnel depth from the ground surface. The settlement was also observed to decrease on moving the tunnels horizontally away from the building at a given depth. Compared to tunnel depth increment, an increase in horizontal distance between tunnels and the building has a greater influence on decreasing settlement. A 45° pressure distribution line was drawn to understand the settlement decrement pattern. Tunnel cross-sectional area overlapping with the influence region of building load was determined for each twin tunnel location. The settlement of the building was found to increase or decrease similar to the changes in the overlapping area. Differential settlements of pile group were observed in all the tunnel locations. But the difference in settlement of individual piles was found to decrease with an increase in the horizontal distance and vertical depth from the pile group.KeywordsPile group settlementExisting building settlementTunnelingNumerical analysisPLAXIS 2D