Seismic response of a shield tunnel crossing saturated sand deposits with different relative densities

Abstract

This study investigated the seismic response of a shield tunnel passing saturated sand deposits with different relative densities. The Dafalias and Manzari model was adopted to capture the cyclic behaviour of liquefiable soil subjected to earthquake excitation. A refined lining model was proposed to simulate the mechanical behaviour of segment joints. A fully fluid-solid coupled analysis was then performed to investigate the seismic response of shield tunnels crossing through adjacent sand deposits with different relative densities. The displacement of segment joints and internal force of lining concrete were found to be prominent near the interface. The structure deformation mode consists of the opening, dislocation, and distortion of ring joints. The complicated tunnel deformation mechanism was then clarified. Comprehensive parametric studies were performed to establish some quantitative relationships between the joint displacement and internal force of segmental linings and the normalized parameters. Apart from soil-deposit interface inclination and cover to diameter ratio, the earthquake magnitude and difference in relative densities had a remarkable impact on the seismic response of the tunnel structure near the interface.