Abstract: This study focuses on tunneling under challenging conditions, particularly with regard to the stress distribution and deformation in the humidity stress field. The swelling phenomenon during tunneling has been treated as a coupled humidity–mechanics process, where the humidity diffusion and stress dilatancy are considered together to obtain stress and deformation fields for tunnels crossing the formations with high swelling potential. A solution to the nonstationary process of humidity transfer has been derived according to Fick’s second law. The swelling pressure has been included in the form of body force, and a non-associated flow rule has been adopted to obtain the analytical solutions. Next, considering the examples of rock tunnels that are excavated in two different quality rock mass, we have investigated the impact factors on stress and deformation in swelling surrounding rock. Numerical results show that the inclusion of the swelling stress increases the plastic zone of the surrounding rock and the maximum stress at the elastic-plastic boundary, whereas the stress convergence has been decreased. After a certain increase in swelling pressure, a tensile stress zone appears in the plastic circle. The deformation of surrounding rock caused by swelling pressure can be much more significant than that caused by in-situ stress. Furthermore, the effect of dilatancy on the deformation rock cannot be negligible especially when the support resistance is small. This paper presents a new possible workflow to quickly evaluate the elastic-plastic stress and deformation of tunnels in swelling surrounding rock.

Key words: deep-buried tunnel, humidity stress field, swelling stress, dilatancy, elastoplastic solution