Integrating National Database of Subgrade Soil–Water Characteristic Curves and Soil Index Properties with Mechanistic–Empirical Pavement Design Guide

The database developed under NCHRP Project 9-23A, Development of a National Catalog of Subgrade Soil–Water Characteristic Curves (SWCC) Default Inputs to Use in the MEPDG, included not only measured soil index properties needed in all hierarchical levels of the enhanced integrated climatic model but also SWCC parameters, which are key in the implementation of Level 1 analyses. A set of maps in portable document format displaying the location of every soil unit identified within the continental United States, Hawaii, Alaska, and Puerto Rico and a simple interface in MS Excel to aid in querying of data were also developed for the project. Under NCHRP Project 9-23B, Integrating the National Database of Subgrade Soil–Water Characteristic Curves and Soil Index Properties with the MEPDG, a second research effort was directed to integrate an enhanced version of the geographic information system–enabled database with the Mechanistic–Empirical Pavement Design Guide. Specifically, NCHRP Project 9-23B aimed at the implementation of an interactive tool that allows the design guide users (currently DarWin-ME users) to retrieve both appropriate soil unit maps and soil properties relevant to a particular user-specified location by entering either state milepost information or geographical coordinates. The final product was integrated into a public website that can be accessed by design guide users, agencies, industry, and academicians through a simple link. Details of the development of this useful search tool and its main features are presented.