Research on Loading and Unloading Rheological Tests and Model Identification of Highway Tunnel Surrounding Rock

On the background of Jiangxi Wuning–Ji'an highway tunnel, the rock triaxial rheological testing machine is adopted to conduct hierarchical incremental cyclic loading and unloading rheological tests on class II, class III, and class IV rock on the tunnel site. Take class II and class IV surrounding rock for example, this paper analyzes the creep deformation rules over time in depth, studies rock rheological properties, and provides the best rheological model of tested rock. According to research findings, deformation of class II and class IV surrounding rock is composed of instantaneous elastic deformation and creep deformation. The instantaneous elastic strain value increases with the increasing stress level and the rock deformation manifests as brittle failure. The generalized Kelvin model is the best rheological model that describes deformation of class II and class IV surrounding rock.