Numerical Study on Dynamic Analysis of River-crossing Large Sectional Shield Tunnel

This paper reports the dynamic analysis of river-crossing shield tunnel for evaluating the performance to resist earthquake. The target project is a large sectional shield tunnel with double deck structure in Nanjing area. The tunnel underground cross complex geological area where acute changing irregular sedimentary layer of soil and rock, with high pressure ground water and so on. This dynamic analysis is performed on smart soil-structure model consists of segments and bolts. Three-dimensional dynamic finite element method(3DFDM) is applied on smart soil-structure model through inputing scientific level waves considering Nanjing regional condition and modified records during 2008 Wenchuan earthquake Ms 8. 0. The results indicate that, (1) the seismic response shown complex formation patterns in soft soil, composite soil and the bedrock., main difference caused complex geological conditions is observed. (2) the maximum stress appears in junction of vertical shaft and shield tunnel, the maximum deformation occurs located in the part near the junction also. (3) in the tunnel, largest stress-value is shown in spandrel and vault, and the maximum deformation is appeared near the vault or the bottom of the arch. (4) the acceleration and displacement in the bolts are effected with the rigid of structure and the mechanical parameters of soil. The stress distribution in bolts is volatility. (5) the influence on dynamic analysis by inputting the Wenchuan wave is larger than the case of Nanjing wave. Our results indicate that the structure will not failure caused by the design acceleration ground motion with 2 percent probabiliy of exceedance in 50 years.