QUASI-STATIC ANALYSIS METHOD FOR SEISMIC EFFECT OF SHEAR WAVES ON SHIELD TUNNEL

Based on the distribution of free-field shear stress around the tunnel, utilizing the elastic center method and the cavity complex variable function, this paper presents an analytic formula for the seismic response of circular deep-buried shield tunnel, where slip and non-slip contacting conditions are imposed to the soil-structure interface respectively and the tunnel is subjected to horizontal shear waves in homogeneous soil. Furthermore, a comparison is made between the equivalent stiffness numerical analytic model and the analytic model considering the effect of joints, showing that the equivalent stiffness quasi-static method and the equivalent stiffness numerical method generate reasonably consistent results in the distribution of shear-wave induced bending moment and axial force as well as the position where the induced bending moment and the axial force reach the maximum. The equivalent stiffness quasi-static method generates the maximum results, followed by the equivalent stiffness numerical method and the analytic model considering the effect of joints. Moreover, considering soil-structure interface slip results in a smaller induced axial force and a larger induced bending moment. In conclusion, the equivalent stiffness quasi-static method takes soil-structure interface slip into consideration, which coincides with practical condition and presents higher safety coefficient and formula simplicity. Consequently, it can be suggested as the anti-seismic design approach for deep-buried circular shield tunnel, and the superposition of the results of constant load static analysis can be conducted to determine the reinforcement design.