Abstract: To control the large squeezing deformation of surrounding rocks with high geostress, the CVISC viscoelasticplastic model formed by the Burgers model and MC plastic body in series is selected for isotropic soft rocks such as mudstone, sandstone, and siltstone based on the previous tunnel cases with large squeezing deformation. The radial displacement of the surrounding rock is divided into instantaneous elasticplastic phase displacement and viscoelastic phase displacement using the independent properties of viscoelastic and elasticplastic elements of the CVISC model. The analytical solutions of radial displacement in the plastic and viscoelastic zones are derived respectively, and the superimposed combination forms the analytical solution of displacement distribution in the surrounding rock. Following this, the radial displacement and stress fields of the surrounding rock are analyzed as a function of time, and the deformation law of the opening is described. The applicability of model is verified with the help of FLAC3D and the theoretical solution of related literature. On this basis, parametric sensitivity analysis of longterm deformation is carried out. The results show that the three most critical parameters in each phase are internal friction angle, cohesion, and Young′s modulus, and the creep parameter has significant sensitivity only in its control phase.

Key words: rock tunnels, large squeezing deformation, viscouselasticplastic analysis, finite difference method