Influence of Poisson’s ratio of isolation material on seismic isolation effect for a shield-driven tunnel in the transversal direction

摘要

In this paper, through numerical analyses of seismically isolatedshield-driven tunnel in the transversal direction, the influence of Poisson’sratio of the isolation material on seismic isolation effect was studied.Conclusions obtained in this study are as follows:(1) It was shown that the isolation layer reduces the bending deformationalong the tunnel longitudinal direction by absorbing theground deformation.(2) The lower the Poisson’s ratio of the isolation material is, thehigher the seismic isolation effect can be obtained. There is athreshold, however, when the Poisson’s ratio of the isolationlayer is lower than the threshold, the isolation effect of seismicisolation does not increase. Under the conditions described inthis paper, the threshold value of the Poisson’s ratio was 0.3.(3) Due to the fact that Poisson’s ratio of isolation material constitutingthe outer periphery of a tunnel affects the apparent springstiffness in the transversal direction, the seismic isolation effectdepends on Poisson’s ratio of isolation material even with thesame Young`s modulus.