Geocharacterization for State Highway 161, President George Bush Western Extension, Dallas, Texas

The State Highway 161 (SH 161) President George Bush Turnpike Western Extension in Dallas, Texas, is a design-build project for the North Texas Tollway Authority (NTTA). The project includes the construction of a 6.5 mile long highway to handle increased traffic in the region. The project includes multiple drilled shaft supported bridges, retaining walls, and design of pavement systems. The subsurface deposits/geologic formations from south to north along the highway alignment include alluvium Fluviatie terrace deposits, the Eagle Ford formation, and the Woodbine formation. Alluvium and Fluviatie terrace deposits consist of gravel, sand, silt, and clay. Eagle Ford formation consists of high-plasticity clays near ground surface. With increasing depth, the high-plasticity clays change into shale. Woodbine formation generally consists of interbedded sands, cemented sands, and mudstones. Characterization of soils and optimization of geotechnical parameters for an economic design was a challenge for this project. Proper evaluation of soil parameters along the highway alignment was performed to design the foundation for various bridges, retaining walls, and pavements. This paper describes the field and laboratory-testing methodologies that were implemented to evaluate and characterize the subgrade of the pavement section along the project alignment.