Abstract: The construction of the deeply embedded tunnel in the soft rock with high in situ geo-stress and its long-term stability evaluation are still the worldwide technical and theoretical challenges. This type of tunnel construction hazard prevention has become the focus of the excavation construction engineering. After the tunnel lining installation, on the one hand, it would be able to carry the creep deformation caused by the low strength of the surrounding rock mass, on the other hand, it also could take the relaxation load caused by the continuous reduction of the self-supporting capacity of the surrounding rock mass with time. Therefore, it is a key developing direction for the design and construction of the tunnel in the soft rock mass with high in-situ geo-stress to reduce the deformation and looseness range of the surrounding rock mass and reduce the load acting on the lining system as much as possible by selecting the reasonable construction methods and support parameters. In this paper, a highway tunnel in the soft rock mass is presented as an example to study its relaxation mechanism through the in-situ geo-stress tests and numerical simulation, which provides a useful exploration for the design and construction selection of tunnels in the soft rock with high geo-stress.

Key words: High In-Situ Geo-Stress, Rheology, Relaxation Effect, Numerical Simulation, Plastic Failure