Hyogo-ken Nanbu Earthquake of January 17th 1995 caused severe damage to underground structures, due to which the seismic problems on them were once again taken seriously. The anti-earthquake code of shield tunnels and bridges was revised, in which two design levels representing low-to-moderate and strong earthquakes are considered. However, under both design levels, the elastic properties of the tunnel-ground system are assumed. This assumption is not realistic under Level-2(strong) earthquakes, because the seismic forces are so strong that the system will behave inelastically. In several relevant design guides, the seismic deformation method is recommended as a design guide for shield tunnel anti- earthquake designing. However, on the modeling of the shield tunnel itself, the method of replacing the lining structure with equivalent stiffness beam is frequently adopted, which means the actually discontinuous lining structure is considered as a continuous and uniform stiffness beam in the same axial direction. But in case of strong earthquakes such a replacement method might ignore the effect of the interaction between the shield tunnel and soil, and that of non-linear features of the ring joints and linings on the seismic response of the shield tunnel. As a result, the internal forces which occur in the shield tunnels will be evaluated excessively. In this paper, the transfer matrix method is employed to derive a calculating method for anti-earthquake designing of shield tunnels. The method is proved to be satisfactory and the above problems are solved.
展开▼
