Suction Distribution of a Wetting Subgrade with Capillary Barrier

Wetting distresses of subgrade( large post-construction settlement,different settlement and reduce of bearing) are usually caused by water migration. However,existing treatments of subgrade are inner treatment,no useful for preventing subgrade wetting. Not only construction cost increaseS,but their long term is not clear. Based on the mechanism of soil deformation and strength in unsaturated condition,moisture migration can be a reference to the design and construction of highway subgrade. Based on moisture migration for unsaturated soils,capillary barrier over subgrade has been proposed in this study. A numerical simulation using CODE_BRIGHT is conducted to compare pore water pressure and volumetric water content of the subgrade with and without capillary barrier. The numerical results show that the subgrade under capillary barrier can reduce the change of suction in the subgrade. Influence region was reduced by 80% and influence depth just reached at the top of the subgrade. Comparing to tradition subgrade,the suction in the subgrade under capillary barrier decreased by 13%. Based on the trend of suction,using the subgrade under capillary barrier can effectively reduce post construction settlement and settlement difference.