During the construction of permafrost tunnels

some extent of surrounding rock will thaw under the effect of construction behavior; it will affect the pressure on support and the convergence of tunnel. An elastoplastic model of surrounding rock of permafrost tunnel under thawing effect is built; and the elastoplastic solution of the model is deduced. In the model

the surrounding rock is divided into frozen zone and thawed zone

considering the frozen zone rock mass as elastic material and the thawed zone rock mass as elastoplastic material. Interaction between the surrounding rock and the support is analyzed under different kinds of surrounding rock and support conditions. The results indicate that the model can represent the characteristics of the interaction between permafrost rock mass and support under thawing effect; and the strength of shotcrete plays an important role in maintaining the stability of permafrost rock mass and controlling the deformation of permafrost tunnel under thawing effect. This model can be used to identify the maximum allowable thawing depth of surrounding rock during construction of permafrost tunnels. Some measures should be taken to control the thawed zone during construction of permafrost tunnels.