Stability evaluation of a tunnel in swelling ground by a simplified multi-scale analysis using a secant stiffness

Abstract

The present study proposes a numerical method to evaluate mechanical influence on tunnel structures caused by severe hygroscopic expansion of the swelling clay minerals. These swelling clay minerals are often called smectite and known to degrade the stiffness of ground due to its own damage. Assuming that this specific physical material behavior can be expressed by an isotropic continuous damage model from engineering viewpoint, we develop a numerical evaluation method for soundness degree of tunnel structures based a decoupling multi-scale analysis. In this context, tunnel structures with surroundings are assumed to be the macrostructure, while material level is to be microstructure. These hierarchically nonlinear numerical analysis needs certain computational efforts. With this background, we formulate a simplified secant solution to solve the nonlinear mechanical problem with a cheap computation cost. The performance of the proposed method is verified by a series of numerical examples.