Abstract: In permafrost regions, canal is usually subjected to the horizontal frost heaving force, which impairs service life of canal. Based on the field test of U-shape subgrade canal in permafrost regions of Qinghai-Tibet plateau and the results of numerical calculation, the influences of canal depth, water content and width of surrounding soil replacement on temperature field and horizontal frost heaving characters were analyzed. The results indicate that U-shape canal depth, water content of soils as well as the width of surrounding soil replacement only have influence on temperature values of surrounding soils, but not on the shape of temperature contour of soils. The horizontal frost heaving force firstly increases and then gradually decreases along the depth of the structure, exhibiting varying values. The maximum frost heaving force occurs at about 1/2-1/3 depth of canal, which has the highest probability to have frost force-induced failure. The horizontal frost heaving force against the trapezoidal canal is about 13%-15% more than against the U-shape canal with the same depth. However, the horizontal frost heaving forces against two different canals have almost the same contour characteristics. The U-shape canal is superior to the trapezoidal structure in the perspective of reducing the horizontal frost heaving force. The more the width of soil replacing, the less the maximum horizontal frost heaving force. For the U-shape canal with 1.7 m in depth, the horizontal frost heaving force changes obviously when the width of soil replacement is from 0 to 2.8 m. However, the change is hardly seen when the width is beyond 2.8 m.

Key words: permafrost regions, canal, horizontal frost heaving force, numerical simulation