Preliminary identification of the failure mode of shallow tunnels in soil subjected to frost heave: Model test and numerical simulation

Freezing action can significantly affect the lining capacity of shallow tunnels in soil. Thus, it is necessary to identify the failure mode of a shallow tunnel in soil subjected to frost heave. Therefore, a thermo-hydro-mechanical coupled finite element (FE) model is established and verified via a model test in the laboratory, in which the similarity ratio of the length is 25. Then, specific consideration is given to the failure mode of the lining structure. The influence of the burial depth on the temperature field and soil-lining interaction are investigated. Meanwhile, the failure mode of the lining subjected to frost heave is discussed. Generally, under the influence of freezing, the normal soil pressure of a shallower tunnel changes more dramatically than that of a deeper tunnel. For the shallower cases (burial depth ≤ 3 m in reality), the outer face of the crown and the inner face of the sidewall are at risk of tensile failure. For the deeper cases (burial depth > 3 m in reality), the outer face of the sidewall and the inner face of the crown are at risk of compression failure.