Study on Seismic Response Characteristics of Shield Tunnel in Soil-Rock Combination Stratum

The sharp change of stiffness in the soil-rock combination stratum is the weak point in the seismic design of the tunnel structure. To explore the influence of soil-rock combination stratum vibration on the shield tunnel, the section of Jinan rail transit line 4 at the Olympic Sports Center is used as the research background. Firstly, the two-dimensional numerical model is established, and the internal force calculation and distribution law of the structure are studied. Then, based on the third similarity theory, the model similarity physical relationship is derived. The shaking-table model test of the soil-rock-structure system is carried out. The seismic response law of tunnel cross-section is studied by the model test and numerical analysis. The results revealed the following: (1) the peak bending moment distribution diagram derived from numerical calculation is consistent with that obtained from the shaking-table model test, which has shown that the numerical and experimental methods are correct, and the research results are available for the seismic resistance of shield tunnels. (2) The deformation, axial force, shear force, and bending moment of the tunnel structure in the soil-rock combination stratum under the action of S-wave change abruptly and significantly at the soil-rock interface section, and the difference in structural stress between the upper and lower sides of the soil-rock interface increased by 65.5%. The excessive stress difference changes the damage mode of the tunnel. (3) The relative difference and abrupt change of bending moment and shear force at the interface is more significant than the axial force, so that the tunnel structure at the soil-rock interface is most prone to bending-shear damage.

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