Abstract: The lining structure of U-shaped canal has favorable integrity and adaptability to frost heave damage; but in winter these canals are still at high risk of frost heave damage. In consideration of the non-linear characteristic of the interface between foundation frost soil and concrete lining as well as the plasticity of frozen soil and concrete lining, we put forward a thermo-mechanical coupling numerical model for U-shaped lining canal, through which the contact mechanical behavior between the foundation and concrete lining such as squeezing, separation and glide can be analyzed. By taking Yuanxiabei main canal in Baojixia irrigation district as prototype canal, we simulated the frost heave damage of the canal in two conditions (considering and not considering the contact between foundation and lining). Results unveil that the simulation results of the model considering the contact are more consistent with the measured values of the prototype, and better explains that the frost heave of U-shaped channel is the smallest at the junction of the channel bottom and the shady slope. The maximum plastic strain of concrete with contact is 3.76 times that without contact. In addition, the normal frost heave force and tangential freeze force considering contact are more uniform, with the maximum values reducing by 1.5~3.0 times. Stress concentration is weakened, which better reflects the interaction between the slip deformation and failure criteria between the concrete lining slab and the canal foundation soil.

Key words: U-shaped lining structure, frozen soil engineering, frost heave damage, numerical simulation, mechanical behavior in contact, Yuanxiabei canal in Baojixia irrigation district