Longitudinal seismic response of non-circular shield tunnels passing through soft-hard stratum

Abstract

With the continuous development of shield tunneling technology, more and more shield tunnels with non-circular cross-section are appearing in the urban transportation system. The seismic performance of these non-circular cross-section shield tunnels should be paid high attention to, especially when they pass through soft-hard stratum commonly seen in engineering. This study conducted a series of numerical calculation cases to analyze the longitudinal seismic response differences between two typical non-circular cross-section shield tunnels, a horseshoe shaped one and a quasi-rectangular one, and a traditional circular cross-section shield tunnel based on a developed 3D full dynamic numerical model. The model described the interaction between segmental ring and straight bolt by using a type of connector element, greatly reducing element quantities and decreasing computational costs. The results show that the soft-hard stratum exhibit non-negligible local site effects under seismic loading; cross-section type of the shield tunnels has a great impact on segmental ring internal force distribution and ring joint opening width; the dynamic responses of the shield tunnel with horseshoe shaped cross-section are always greater than those of the other two shield tunnels; the maximum bolt response always occurs at the crown and invert of ring joints under longitudinal seismic excitation, therefore, these two critical positions should be prioritized for seismic reinforcement.