Measurement and Analysis of Moisture Migration Characteristics in Subgrade of Excavation Section

Abstract

To cope with the phenomenon of moisture imbalances in subgrades due to excavation, the resistivity of different excavation subgrades (deep excavation section, shallow excavation section, and cut-and-fill transition section) at different vertical depths pre- and post-excavation of blind drains were measured using temperature and resistance sensors laid in test sections of the Zhangjiakou-Zhuozhou expressway project. The moisture migration characteristics in excavation subgrades were analyzed by developing the relation between resistivity and moisture content from laboratory experiments. The analysis results show that (1) the moisture contents in subgrades in late autumn and early spring increases with an increased excavation depth, which is due to the combined effect of the temperature and water supply from excavation slopes; (2) blind drains and the roadbed replacement depth contribute to the suppression of moisture migration in excavation section subgrades, which can improve the work state of the subgrade; (3) summer rainfall significantly influences moisture migration in deep excavation section subgrades and cut-and-fill transition section subgrades; the moisture content in summer significantly increases compared with that in the other seasons; the influence of seasonal factors on moisture migration in deep excavation section subgrades is significantly stronger than that in cut-and-fill transition section subgrades.