In Situ Testing and Evaluation of Moisture Content in Existing Sub-Grade

The bearing capacity of subgrade soils, which is a critical parameter for assessing pavement conditions and guiding the type and extent of maintenance and rehabilitation (M&R), is greatly influenced by soil water content. In this study, a case of long-term spatial distribution of moisture content in existing cohesive subgrade in Shanghai was investigated. The in-situ testing data revealed significant variations in the water content of the sub-asphalt soils layers in both the horizontal and vertical directions. The equilibrium moisture contents (EMC) beneath pavement were calculated based on unsaturated soil theory and Fredlund & Xing equation was chosen as the soil-water characteristic curve (SWCC). Comparison of water content estimates from investigation and from prediction shows that, the relative elevation of groundwater table (GWT) is an influential factor controlling moisture distribution in subgrade, but areas with high water content immediately beneath pavement mainly reflect the inefficacy of pavement drainage systems.