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.