A NON-LINEAR BACK-ANALYSIS PROCEDURE FOR SHALLOW TUNNELS EXCAVATED IN UNCONSOLIDATED GROUNDS

Abstract

The excavation of shallow tunnels in unconsolidated grounds causes non-linear displacements in many cases, which leads to a serious problem. In this paper the authors defined and analyzed these displacements by reducing the shear-stiffness related to the shear-strain in geo-materials. They applied this procedure to simulate actual soil behaviors, and succeeded to demonstrate the practical applicability. Further the authors analyzed the non-elastic volumetric changes together with this procedure and concluded that the vertical displacements between ground surface and tunnel crown are more precise with the measurements than the case using only anisotropic damage parameters.