Tunneling Using TBM in Sandy Soil and its Effect on Deep Foundations

With the increasing demand to alleviate traffic congestion, subway tunnels are becoming a prominent transportation solution. However, tunnel construction induces soil movement, potentially impacting the stability of nearby structures. In the current study, the impact of tunnel construction on nearby deep foundations has investigated through numerical modeling (PLAXIS 3D). First, surface settlements reported in a case history of tunneling boring machine (TBM) movement during the construction of Metro line 2 in China has used to validate the developed numerical model. Second, analytical methods to estimate the required parameters for the simulation of TBM movement in the finite element program were investigated and a sensitivity analysis was conducted to study the effect of varying each parameter on the evaluated surface settlements. Thus, the recommended methods to be followed in selecting the TBM simulation parameters were concluded. Finally, the effect of the TBM movement on deep foundation behavior (a group of piles) in sandy soil has been investigated. By varying the location of the TBM under the tip and beside the pile group, the variation of bearing reaction, total axial load, settlement of the piles, and pile cap deformations have been evaluated during the TBM movement.