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Abstract
This research involved a comprehensive experimental program was carried out to study compaction characteristics and associated engineering properties of test soils from three actual NCDOT highway projects located within the coastal geologic region of NC. The laboratory testing program helped determine engineering properties such as shear strength parameters, Su, friction, cohesion, and stiffness, as well as classification under United Soil Classification System (USCS). The information gathered from this testing was used to analyze the performance of different highway embankment geometries in terms of slope stability. This analytical component was used to assess the suitability of the current NCDOT selection criteria and to develop recommendations toward an improved criterion. A survey of current practices, in terms of material selection for highway embankments was also carried out as part of this research to set a guidepost showing how NCDOT embankment material compares to the rest of the nation. The slope stability analyses involved using the slope stability analysis software Slide 7. The different values of the factor of safety computed as a function of engineering properties based on material type, compaction characteristics, and embankment geometry were used to perform a statistical regression analysis with the statistical analysis software SPSS. The regressions obtained were found to be useful to estimate an overall embankment stability number or index that can be used as a basis for an improved material selection process.