EXPERIMENTAL STUDY ON THE EFFECT OF NONLINEARITY OF GROUND ON SHEAR STRAIN RATIO IN CUT AND COVER TUNNEL DURING THE EARTHQUAKE

Abstract

 The interaction between the structure and surrounding ground should be appropriately evaluated in the seismic design of cut and cover tunnels. In particular, the shear stiffness ratio (G_g / G_s) between the structure and the surrounding ground is a crucial parameter to evaluate the shear strain ratio (shear strain of the structure γ_s / shear strain of the ground γ_g). However, the effect of the nonlinearity of ground on these relationships has not been clarified. In this study, a model experiment using a small shear tank was conducted using an aluminum rod laminated model ground, which can simulate the nonlinearity of the ground. There are three experimental cases with different structural stiffness. The results are compared with elastic FEM analysis. It is confirmed that the effect of nonlinearity of the ground on the shear strain ratio during an earthquake can be evaluated by modeling the ground with equivalent linear stiffness under the condition of a large shear stiffness ratio.