Abstract:

In order to explore the stability problem of cold-region circular tunnels subjected to the frost heaving force action, based on a model of circular tunnels considering the effect of the frost-heaving force, the elastic-plastic solutions of radial stress, tangential stress, plastic zone radius and loose zone radius were deduced with the generalized Hoek-Brown strength criterion and the internal boundary stress conditions (σ_r|_r=r1=σ_r1). Based on a project case, the result from this work was compared with those of the existing method (namely the method of external boundary stress conditions), which verified the feasibility of this method. The results show that the geological strength index, rock mass constant, uniaxial compressive strength, disturbance coefficient, tunnel excavation radius and frost heave force have significant effects on the radial stress, tangential stress, plastic zone radius and loose zone radius of cold-region circular tunnels. Among them, the disturbance coefficient has a significant effect. Compared with the ideal blasting condition (D=0.7) and the case without disturbance (D=0), the relative error of the results reaches 32.2%-55.8%. The influence of frost heaving force is very significant. When the frost heaving force varies from 0 to 1.02 MPa, the relative error of the result can reach 507.1%. If the influence of frost heave force was ignored, the radial stress and tangential stress in the plastic zone would be seriously underestimated, and the range of the plastic zone and the loose zone would be substantially overestimated.

Key words: frost heaving force, cold-region tunnel, boundary stress condition, generalized Hoek-Brown strength criterion, elastic-plastic solution