Effect of TBM tunneling in sandy soils on twist behavior of an existing raft foundation

ABSTRACT: Constructing new underground tunnels is a necessity in urban areas to resolve traffic congestion problems. The new tunnels may pass underneath or nearby existing buildings; therefore, the structural safety of the foundations of these buildings should be evaluated. This study focuses on the effect of the TBM tunnel advancement on the twist deformation of an existing raft foundation. The 3D nature of the TBM construction process has been simulated using PLAXIS 3D software. In order to validate the results of the numerical simulation, the resulted settlement trough has been compared to the measured field settlement trough of a selected case study (Second Heinenoord Tunnel in the Netherlands). In the current study, an extensive 3D parametric study is conducted to check the effect of related parameters on the raft twist deformation. The studied parameters include; tunnel cover (Z), skew angle between raft and tunnel (i), raft thickness (d), and raft weight (w).