Abstract: To investigate the combined effects of ice cover and longitudinal joints on the mechanical behavior of frost heave in canals during stable freezing periods, a frost-heaving mechanical model for lined canals with longitudinal joints is proposed. This model is based on the discontinuous elastic foundation beam theory with variable stiffness coefficients under multiple loads, incorporating the concept of the finite beam element method. By introducing auxiliary functions, a unified solution for the deformation of beam elements under different loading conditions is achieved. Using an engineering case study, the frost heave mechanical response of the canal lining plate is analyzed, and the influence of groundwater depth and of ice thickness on the normal displacement and of stress of the lining is further explored. The computational results show that in the region above the ice cover, the root mean square errors of the lining frost heave deformation calculated by the proposed model and by the traditional Winkler model, relative to the measured values, are 0.17 cm and 0.39 cm, respectively; that in the region below the ice cover, the root mean square errors of the calculated values obtained using the proposed model, the Winkler model, and the finite difference method are 0.13 cm and 0.18 cm, respectively. The model proposed provides a better approximation to the actual conditions compared to the traditional Winkler model. The beam elements directly subjected to ice loading exhibit larger bending moments and upper surface stresses, while adjacent beam elements show smaller bending moments and stresses. The peak stress on the upper surface and the stress-exceeding intervals are located on the frozen soil side near the ice cover, which aligns well with the actual cracking positions. Due to the presence of longitudinal joints, the distribution of bending moments and upper surface stresses exhibits fluctuations, with zero bending moments at the joints. As the groundwater depth decreases, the frost-heaving deformation of the lining slab in the area above the ice cover increases rapidly, and the range of displacement exceeding the limit also expands. With increasing ice thickness, the frost heave deformation in the critical areas decreases, while the upper surface stress increases. The static ice pressure and ice thickness exhibit an approximately power-law relationship. This research is conducive to predicting the risk of frost-heaving damage to winter water conveyance canals under the combined effects of the subsoil frost heave and of ice cover loading.