Dynamic sub-structure method for longitudinal seismic response of large-diameter shield tunnel through the complex strata

Based on the deficiencies of the generalized response displacement method and the integral response displacement method for longitudinal seismic analysis of the shield tunnel, the dynamic sub-str1cture analysis method for longitudinal seismic response of a large-diameter shield tunnel crossing the complex soil layer is proposed. The feasibility and superiority of the dynamic sub-structure analysis method are explored by comparing it with the calculation results of the three-dimensional (3D) soil-underground structure interaction model. Then, a finite element refined 3D model of the 2.7 km Suai submarine shield tunnel is established by using the proposed method, and the longitudinal seismic response of the large-diameter shield tunnel crossing complex soil layers is simulated and analyzed. The research results indicate that the proposed dynamic sub-structure method has clear concepts, accurate calculation results and high efficiency to simulate the dynamic soil-tunnel interaction, which can avoid the error effect of the equivalent soil spring used in the generalized response displacement method. At the same time, this method can consider the seismic effect of the complex soil layers which has been avoided by the generalized response displacement method and the integral response displacement method. Also, the calculation results by the proposed method can comprehensively present the typical earthquake damages of shield tunnels crossing the wide river valley or the strait. It proves that it is not appropriate to simplify the longitudinally of the shield tunnel into a straight line, as doing so would neglect the influence of the longitudinal slope of complex river valleys or the straits. Also, the longitudinal seismic response of the shield tunnel is more sensitive to low-frequency seismic waves and the bolts are more susceptible to seismic damage compared to the segment opening.