Dynamic Response and Mitigation Techniques for a Shield Tunnel Passing Through Saturated Sand and Clay Deposits

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ABSTRACT The geological conditions are extremely complex in the coastal and riverfront cities in China, some shield tunnels are designed to inevitably pass through various saturated strata, while the dynamic response of tunnel structure passing through multiple saturated soil layers remains unclear. This paper investigated the dynamic responses of a shield tunnel passing through saturated sand and clay deposits under transverse and longitudinal earthquake excitations. The practical two-surface plastic model and hysteretic model were adopted to capture the saturated sand and clay, respectively. The sophisticated tunnel model was proposed to simulate the cyclic mechanical behaviour of segment joints. The numerical results reveal that tunnel structures near the soil interface present uneven upward deformation, resulting in a significant increase in lining force and joint displacements. Comprehensive parametric studies indicate that earthquake magnitude, clay type, sand density, and interface inclination have a major impact on the dynamic response of shield tunnels near the soil interface. It was determined that the grouting measure and rubber buffer layer could effectively alleviate the differential uplift of tunnel segments and the displacement of segment joints near the interface. The research results could serve as a theoretical reference for the purpose of seismic design of underground structures.