Multiscale stability analysis of a tunnel in swelling rockmass applying secant stiffness

Damage of tunnels often occurs in Japan caused by swelling smectite rockmass. For an effective countermeasure against the damage, mechanical interaction between tunnel lining and swelling rock mass are analyzed by a two-scale analysis based on a homogenization theory in this study. In the microscopic scale, swelling of smectite minerals and damage process of surrounding intact rocks induced by the swelling of smectite minerals are analyzed by a 3D continuous damage model. This microscopic analysis provides the averaged volumetric change and the damaged macroscopic stiffness of the representative volumetric element (RVE) of rock mass. In the macroscopic scale, therefore, stress distribution within/around the tunnel lining can be reasonably analyzed by using the averaged secant stiffness and its volumetric strain of the RVE. The mechanical interaction between the tunnel lining and swelling rock mass is discussed and examined as some case studies are carried out.