Analytical Viscoelastic Solution for Double-lining Tunnel Under a Non-hydrostatic Stress Field Considering Creep Characteristic of Shotcretet

When constructing tunnels in rheological rocks, the rock creep continuously increases the support structure load. At the same time, due to the influence of the existing environment, shotcrete also undergoes creep, which leads to a complex mechanical mechanism between structures and surrounding rock. Existing research findings only analyze the above issues in the hydrostatic stress field, and this issue has not yet received attention for tunnels built in the non-hydrostatic stress field. This article proposes an analytical solution using complex variable functions and Laplace variation, taking into account the rheological properties of surrounding rock, non-hydrostatic stress field, creep characteristics of shotcrete, and double lining. The paper simulates the rheological properties of shotcrete and rock uses Kelvin-Voigt. Using displacement coordination equations and stress boundaries between surrounding rock, shotcrete, and lining, the tunnel mechanics mechanism can be solved. This article uses both continuity and numerical simulation methods to prove the accuracy of analysis results, and indicates shotcrete creep will reduce its own bearing capacity and displacement constraint capacity while causing an increase in the secondary lining load. The faster the creep rate of shotcrete, the faster the tunnel deformation rate; the smaller the shotcrete creep modulus, greater the tunnel deformation. Therefore, for tunnels located in non-hydrostatic stress fields, the design of secondary lining should consider the creep of shotcrete to prevent the failure of support structures during tunnel operation. Finally, practical cases have proven that the analytical method proposed in this article has the advantages of efficiency and convenience.