Numerical Simulation Study on the Seismic Response of Shield Tunnels in Liquefiable Interlayer Site

Abstract

Soil liquefaction under seismic loading poses a significant threat to the structural safety of shield tunnels, especially those located in liquefiable interlayered grounds, which are more prone to severe damage. This study employs the CycLiqCPSP model to develop a two-dimensional saturated soil-shield tunnel interaction framework, examining seismic responses of shield tunnels under five spatial configurations of liquefiable soil layers. Resonant column tests and triaxial tests were conducted to calibrate the constitutive model parameters for liquefiable soils in the Beijing area, and the accuracy of these parameters was validated through element test simulations. The results indicate that, compared with shield tunnels in homogeneous liquefiable soils, the spatial distribution of liquefiable interlayers has a significant impact on the seismic response of the soil-structure interaction system. This influence leads to increased deformation, internal forces, and significantly higher damage levels in the tunnel structure. When the tunnel's base crosses the liquefiable layer, lateral deformation is notably amplified, causing severe structural damage and representing the most adverse seismic design scenario. Additionally, during seismic events, drainage channels may form in the middle section of double-track tunnels, heightening the risk of liquefaction. The study also reveals that the internal forces and deformations at the tunnel's haunches and toes are significantly higher than at other locations, necessitating special attention to these areas for potential damage. These findings offer essential theoretical guidance and scientific insights for the seismic design of shield tunnels in liquefiable interlayered grounds under strong earthquakes.

Keywords

elastic-plastic contitutive model / liquefied interlayer site / post-liquefacion deformaion / seismic response / shield tunnel

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