FE analysis of the influence of sliding on the seismic strain transfer ratio between the ground and cut and cover tunnels in contact with bearing stratum

Abstract

In the seismic design of box-shaped cut and cover tunnels, the effect of interaction between the box structure and the ground must be considered. The ratio of the average shear strain of the entire box γ s to that of the ground γ g (strain transfer ratio γ s / γ g) is one of the most important parameters in the seismic design of tunnels, considering that the shear deformation of the ground can significantly damage tunnels. However, this strain transfer ratio γ s / γ g varies significantly depending on the ratio of the shear stiffness of the box Gs to that of the ground Gg (shear stiffness ratio Gs / Gg). This study presents the results of the FE analysis under the condition that the box is in contact with the bearing stratum, which has not been reported before. Although the ground is assumed to be elastic, joint elements are used to compare the effect of the sliding behavior. The results showed that for Gs / Gg < 1, the contact between the box bottom and bearing stratum reduced the strain transfer ratio γ s / γ g, whereas the influence of sliding behavior was almost insignificant. When Gs / Gg > 1, the contact between the box bottom and bearing stratum increased γ s / γ , whereas the sliding behavior reduced γ s / γ g. These results provide important information for the physical model test results. Furthermore, the author's research group conducted model tests using aluminum rods, and the results will be compared to the results of future model tests.