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The damage caused by the frost heaving pressure on the surrounding rocks and lining structure of cold-region tunnels is always common, which can seriously threaten the safety and stability for cold-region tunnels. Although many achievements of frost heave pressure model have been obtained, two factors have been often ignored, which are in-situ stress and freeze-thaw cycles. Therefore, the calculation mechanical model of cold-region tunnels is established and the expression of frost heaving pressure considering frost heaving effect and in-situ stress is derived based on the elastic theory. The relationship between the elastic modulus of surrounding rocks and the number of freeze-thaw cycles was fitted by experimental data and the calculation formula of frost heaving rate of rocks considering their porosity change caused by freeze-thaw cycles is derived. Based on that, the calculation method of frost heaving pressure considering in-situ stress and freeze-thaw cycles is proposed. The example analysis results show that frost heaving ratio and frost heaving pressure gradually increase with freeze-thaw cycles, which are eventually subjected to a steady value. Simultaneously, the frost heaving pressure acting on lining increases with in-situ stress for tunnels in cold regions and some effective insulation measures should be applied to prevent frost damage. [ABSTRACT FROM AUTHOR]

Precise evaluation of the frost heaving force and surrounding rock plastic zone is an important basis of the prevention of freezing damage in cold-region tunnels. The temperature gradient along the radial direction of cold-region tunnels surrounding rock results in the dual non-uniform frost heaving of surrounding rock, namely, the gradual change of frost heave ratio along the radial direction and the unequal frost heaving deformation in the circumferential and radial directions. A new elastoplastic solution of tunnel frost heaving force considering double non-uniform frost heave and intermediate principal stress was derived based on the elastoplastic mechanics theory, thick-cylinder theory, and unified strength theory to better guide the frost resistance design of tunnels in cold regions. The rationality and advantages of the unified plastic solution of tunnel frost heaving force were verified by model tests and engineering examples. Results showed that the theoretical calculation value of frost heaving force was in good agreement with the measured value. When the gradual change in the frost heave ratio of surrounding rock in the radial direction was ignored, the frost heaving force and radius of the surrounding rock plastic zone were large and conservative. The solution in this paper can accurately evaluate the tunnel frost heaving force and surrounding rock plastic zone. Finally, this paper studies the influences of intermediate principal stress coefficient, the frost heaving coefficient of unit temperature of frozen surrounding rock, non-uniform frost heaving coefficient in different directions, and maximum freezing depth on the evolutionary law of frost heaving force and plastic zone of cold-region tunnels are studied. • A dual non-uniform frost heaving model of cold region tunnels is proposed. • Use temperature gradient to describe the non-uniform frost heave of the surrounding rock. • An elasto-plastic solution for frost heave force based on dual non-uniform frost heave is derived. • Theoretical solutions, model test results and engineering tunnel cases were compared. [ABSTRACT FROM AUTHOR]

Frost heave in cold-region tunnels is caused by complex water-ice phase changes with coupled heat and moisture transfer, which will lead to frost damage and thus threatens the structural stability and traffic safety. To describe the frost heave force, a new model is established for the coupled heat and moisture transfer in the freezing surrounding rock, which consider the major influence factors of the three primary frozen theories for cold-region tunnels simultaneously. An analytical solution for the coupled multifactor is proposed, in which the calculated parameters could be classified into three categories: 1) the frost heave ratios(α fr , α mr , α i); 2) the geometric parameters(R , T mr , T i); and 3) the confinement strength(K r , K fr , K mr , K l , K i). All parameters are studied, in which frost depth is deduced by comprehensively considering the ice content, thermal coefficient and freezing index, and a new method based on a difference value method for the equivalent elasticity coefficient of the lining or ice is also proposed. Furthermore, the method is validated in the Daban Mountain tunnel, and the results have indicated that the proposed analytical solution can accurately reflect frost heave force. • A model for frost heave force was established from the coupled heat and moisture transfer in cold-region tunnels. • Parameters to frost heave force were studied in detail to determine the distribution range or the calculation method. • Frost depth was deduced by comprehensively considering the ice content, thermal coefficient and freezing index. • A method based on a difference value method for the equivalent elasticity coefficient of the lining or ice was proposed. [ABSTRACT FROM AUTHOR]