Numerical modeling of moisture migration in high-speed railway subgrade

During the long-term service life of high-speed railway, increase of moisture in the subgrade will degrade the performance of the high-speed railway. Cracks on the surface of the subgrade are found in some existing high-speed railways and water will infiltrate into the subgrade through the cracks in rainy days. A numerical model using Geo-studio Seep/W is established to simulate moisture migration in the subgrade. Two cracks are set in the edges of the concrete base. The moisture migration in the subgrade within two years has been calculated. The results indicate that “saturation zone” occurs in the subgrade. The volumetric water content ranges from 10% to 27% in the surface layer and from 20% to 26% in the bottom layer, respectively. The seepage line reaches at the interface of bottom layer and subbase layer after 184 days and stays stable in the remaining 546 days. This is explained by the reason that water can only permeate into the subbase layer with an extremely low seepage velocity and then it accumulates at the bottom of subgrade bottom layer. And this accumulation area has a volumetric water content value of 28%, slightly higher than that in other areas of subgrade bottom layer in the final period