Abstract: Tunnel excavation with large depth will be confronted with huge tectonic stress and self-weight stress, and the geostress cannot be ignored in the design of excavation. According to theoretics of unloading and rheology, inversion of rheological parameters were conducted based on indoor rheological tests, and furthermore, the creep deformation and plastic zone of surrounding rock at different depths before and after lining were compared and analysed by ANSYS and FLAC. Results reveal that as buried depth increased, the tunnel’s unloading effect became more obvious; a pressure arch occurred and then disappeared under the joint action of unloading and surrounding rock; and the tunnel’s horizontal displacement increased, hence lateral deformation became a controlling factor of tunnel’s stability.

Key words: tunnel, unloading caused by excavation, surrounding rock, lining, rheology, plastic zone, stability