Numerical studies on tunnel floor heave in swelling ground under humid conditions

Abstract

A humidity diffusion based numerical model is proposed to simulate the floor heave processes of swelling rock tunnel when it exposed to high humidity. The phenomenon of swelling in tunneling is treated as a humidity–mechanical coupled process, i.e. the stress redistribution as well the water vapor diffusion around the tunnel is taken into account. This allows one to model the observed floor heaves realistically without considering the complex chemical processes induced by water–rock interaction. Furthermore, the development of heave and pressure over the course of time can be studied. The swelling rock is considered as an elasto-plastic material with damage threshold, which allows one to predict the large heaves of a tunnel floor that are often observed in-situ. The relationship between the mechanical damage and humidity diffusion are discussed at the mesoscopic level. By studying the influence of parameters in the numerical model on the floor heave behavior, the time-dependent deformation and failure processes of tunnel under high humid condition are discussed in detail. The deformations at the floor level are larger than that of sidewalls interpreted here as a consequence of different humid boundary conditions. The numerical results provide a better understanding of time-dependent behavior of floor heave of tunnel under the high humid condition.