Soft soil layer-tunnel interaction under seismic loading: Fid-Bau Portal

Soft soil layer-tunnel interaction under seismic loading

Sun, Qiangqiang / Dias, Daniel / Ribeiro e Sousa, Luis

Highlights • Three soft soil layer-tunnel intersecting scenarios are considered. • The effects of the soft soil layer relative stiffness, thickness, flexibility ratio, and nonlinearity are presented. • The lining forces and deformations in terms of distributions and magnitudes are presented. • Possible explanations for the obtained response are provided.

Abstract Understanding the soft soil layer-tunnel seismic interaction in the multi-layered ground is an important issue for a safe seismic design. However, this issue remains unclear since most of the previous studies considered homogeneous grounds. In this regard, the paper aims at investigating the seismic behavior of tunnels when they intersect a soft soil layer. Three soft soil layer-tunnel intersection scenarios (i.e., at the crown, springline, and invert) are respectively considered based on an academic case. Two-dimensional numerical analyses are performed for a wide range of soft soil layer thicknesses and shear wave velocities, assuming various flexibility ratios. The effect of soil nonlinearity is also involved. The results reveal that the presence of a soft soil layer generally increases the internal forces and deformations, particularly when a very soft soil layer passes through the flexible tunnel at the springline. The findings of this work may have a certain reference value for seismic design practice of tunnels.