<p>Following continuous progress to enhance the accuracy of prediction of the long-term behavior of tunnels via using more appropriate constitutive models, this paper adopts a non-linear stress–strain law in plastic zones rather than the general perfectly plastic behavior. For this aim, first of all, a theoretical solution is developed in which the viscoelastic-plastic rheological model (consisting of the Burgers model with either the generalized Hoek–Brown or Mohr–coulomb failure models connected in series) is assigned to the rock mass. In this model, when stresses do not satisfy these failure criteria, the rock mass behaves viscoelastic behavior with the Burgers rheological model. If stresses exceed the strength of rock mass, a plastic zone will appear. In this zone, assuming the non-linear stress–strain relationship, the values of mechanical parameters are updated based on the plastic shear strain. The result indicates the non-suitability of assigning the perfectly plastic behavior to the rock mass. Furthermore, it is found that the Non-linear post-peak behavior of the rock mass has a remarkable effect on the tunnel response. In the next step, the problem is simulated by FLAC^3D software with the same assumptions made for the proposed analytical model. Then, the proposed approach is verified using the existing analytical methods. Also, in another effort, the obtained displacements in the analytical method are compared with measured displacements of a real case (Saint Martin La Porte access gallery). It is found that a good agreement exists between the results. The numerical simulation is extended via assigning the CVISC elastic-visco plastic rheological model (the Burgers model connected in series with a slider for prediction of failure) to the rock mass. The results demonstrate that it is possible to disregard the rheological behavior of the plastic zone without suffering a significant loss in accuracy.</p>