Civil Engineering Association

A National Database of Subgrade Soil-Water Characteristic Curves and Selected Soil Properties for Use with the MEPDG

This final report describes the approach followed to create the national database of unbound material properties required as input in the AASHTO Mechanistic‐Empirical Pavement Design Guide (MEPDG). This database contains measured index soil properties as well as Soil‐Water Characteristic Curve (SWCC) parameters, for use at the three optional hierarchical levels of the analysis implemented in the MEPDG. This database is based and has been developed on soil properties directly measured in the field for agricultural and geotechnical (pavement) engineering purposes to depths up to 100 in. (8 – 9 ft). The database comprises 31,100 soil units distributed in more than 9,800 soil profiles covering the continental USA, Hawaii and Alaska, and Puerto Rico. Data from the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS) was downloaded and summarized in both tabular and spatial files. The tabulated data was organized by soil profiles, each of them comprising one or more soil units. The spatial data allowed for the creation of 814 maps within the United State and Puerto Rico. Finally, a user interface was created in Excel© to allow searching for specific locations within a State, by using the maps created in the project.