挖方路段路基水分迁移特性测试与分析

Measurement and Analysis of Moisture Migration Characteristics of Excavation Subgrade

针对公路因开挖而出现的路基水分失衡现象,在张家口—涿州高速公路工程选取试验段埋设温度和电阻传感器,测试不同挖方深度路段(深挖、浅挖和填挖过渡段)路基在开挖渗沟前后不同深度处的电阻率;通过室内试验建立电阻率和含水率之间的关系,分析了挖方路段路基水分迁移特性。分析表明:随着挖方深度的增加,深秋与初春的含水率差值△W不断增大,即在挖方边坡水分补给和温度共同作用下,水分迁移的强度随着挖方深度的增加越来越强烈;渗沟和一定深度的换填有助于抑制挖方路段水分迁移作用,改善路基工作状态;对比填挖过渡段和深挖方路段季节性水分迁移,夏季降水对2处路段影响显著,所测土基含水率较之其他季节明显增大,季节性因素对深挖方路段水分迁移强于填挖过渡段。

To cope with the phenomenon of subgrade moisture imbalances due to excavation, the resistivities 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 drain are measured by temperature and resistance sensors laid in test road section in the Zhangjiakou-Zhuozhou expressway project. The moisture migration characteristics of excavation subgrade is analyzed by the relation between resistivity and moisture content established by laboratory experiment. The analysis result shows that （1） the difference of late autumn and early spring moisture contents increases with the increase of excavation depth, which means that the moisture migration intensity increases with the increase of excavation depth under the combined effect of cut slope water supply and temperature; （2） blind drain and a depth of cut-and-fill replacement contributes to the suppression of moisture migration of excavation section and to improve the work state of subgrade; （3） there is a significant impact of the summer rainfall on the seasonal moisture migration of the deep excavation section and the cut-and-fill transition section, the measured moisture content of soil significantly increases compared to the other seasons, the influence of seasonal factors an moisture migrationof deep excavation section is significantly stronger than that on the cut-and-fill transition section.