Enhancing Tunnel Stability Under High Ground Stress: Rheological Analysis and Support Strategies

Aiming at the large deformation of surrounding rock during tunnel construction under high ground stresses, this paper takes a high ground stress soft rock tunnel project in Yunnan Province as the background. According to the uniaxial and triaxial compression and creep experiments of rock, a creep constitutive damage model suitable for this project is built. Then, this creep damage constitutive model is applied in FLAC3D numerical analysis software to analyze the deformation characteristics of each monitoring point of the tunnel and the plastic zone change characteristics of the surrounding rock during tunnel excavation during tunnel excavation, and a support optimization scheme is proposed for the project. The results show that the numerical calculation results are consistent with the actual monitoring data, which confirms the accuracy and rationality of the proposed creep constitutive model. In addition, when the tunnel is under different stress states, the location of the largest displacement deformation of the tunnel varies. Under self-weight stress, the maximum deformation is located at the vault and invert, while under tectonic stress, the maximum deformation is located near the spandrel and haunch. Finally, according to the numerical calculation results under different working conditions, the optimized support schemes for the two working conditions are proposed respectively. Adopting combined group anchor surrounding rock reinforcement technology and constructing the inverted arch pipe pile, so that the shallow surrounding rock and deep surrounding rock together to form a complete system of coordinated deformation, and the use of large stiffness double-layer primary support technology to improve the ability of the primary support to absorb the deformation, which effectively reduces the creep characteristics of the surrounding rock, to control the large deformation of the tunnel. The research results of this paper can provide a reference for the support design of high geostress tunnels.