Abstract:
The uncoordinated deformation between the contraction around a canal and the rigid lining caused by the normal frost heaving of the canal foundation soil is the main cause of the frost damage to the lining. Setting longitudinal joints is the main measure to prevent frost damage in the specification, but their positions and widths cannot be determined. In this paper, the frost heaving characteristics of the open and semi-open environments were considered, and a mathematical model for calculating the frost shrinkage around canals of various typical sections was established according to the deformation coordination conditions. Subsequently, the calculation formulas of the shrinkage around canals were derived and then verified by the canal frost heaving model with moisture-heat-mechanical coupling. Finally, the distribution and sensitivity of the freezing shrinkage around the canal and the method were developed to determine the layout and minimum width of the longitudinal joint. The results show that: the freezing shrinkage sensitivity of section shape is trapezoid, parabola, trapezoid with arc bottom/trapezoid with arc toe/U-shape from high to low. When
α is less than 55° under a semi-open system or
α is less than 70° under an open system, the freezing shrinkage of a parabolic canal is larger than other forms. Whether the curvature of the section is continuous determines the variation range of the freeze-shrinkage rate. The freezing shrinkage rate of a wide-shallow canal is less than that of a narrow-deep type one, and a wide-shallow trapezoidal section with arc toe or arc-bottom has the most uniform freezing shrinkage distribution and the best frost heaving resistance. The parabolic shape is only suitable for narrow-deep sections. To reduce the frost damage caused by uncoordinated deformation, the joint should be set at the section with a sudden increase of freezing shrinkage rate, and the joint positions of canals with different section shapes are as follows: slope toe for the trapezoidal canal, bottom center for the parabolic canal, and junction of the straight and curve lines for the trapezoidal canal with arc-bottom or with arc toe or U-shape canal. The research results can provide a theoretical reference for the anti-frost heave design of canals in cold regions.