Mechanism of Groundwater Migration in the Subgrade in a Seasonally Frozen Soil Area

摘要

The migration of groundwater often results in subgrade damage such as fracturing, pavement pumping, and cracking in seasonally frozen soil areas. Indoor tests were performed to simulate moisture migration in different soil types usually found in seasonally frozen soil areas. The results indicate that the moisture migration rate of the wetting front in clay is the fastest, followed by that in fine sand and silt. In addition, the migration height of fine sand is much lower than that of both clay and silt, whereas the water flux is larger than that of clay and silt. Moreover, under a freeze-thaw cycle, the trends of water content change and temperature distribution of the three samples at the initial state and final state were similar. Based on the gravity, matric, and temperature potentials, the moisture migrated continuously throughout the freezing process, and the temperature gradient could cause moisture to migrate faster than usual. According to the mechanism of moisture migration in the indoor tests, a case study and field test of the Jixi-Nehe Highway were undertaken in Heilongjiang Province, China. The field test results show that the moisture migration in the seasonally frozen region is consistent with the results of the indoor tests. Highway construction could significantly increase the water content of soil at the original position in the subgrade. Some measures were put forward to protect the subgrade from damage caused by moisture migration.