Performance of the highway embankments has been investigated based on two main concerns; slope stability and deformation. To examine embankment performance, parameters obtained from both total stress analysis (TSA) and effective stress analysis (ESA) have been considered, that is stability and deformation have been each investigated under two states of TSA and ESA. This also necessitates that soil strength properties are obtained at both TSA and ESA conditions. The scope considers only failures and settlements related to compacted embankment and not due to poor foundation soil conditions. A set of unconsolidated-undrained (UU) triaxial tests has been used to obtain total stress soil strength properties, and a set of consolidated-undrained (CU) triaxial tests with pore pressure measurements has been considered to achieve effective stress soil strength properties. Sixteen embankment geometric sections have been considered in total. For the highway embankement deformation analysis, two-dimensional plane strain conditions were assumed. Among all cases, not even one case showed TSA factor of safety lower than the minimum value of 1.3. In many of these cases FS is well above the minimum value. Results of the stability analysis based on ESA parameters were completely different from those of obtained using TSA parameters, as in the effective stress stability analyses many cases were found having FS lower than 1.3. For the effective stress slope stability analysis, shallow failure must be checked as it is a case with high possibility. There are some findings that might give grounds to the idea that soils with higher PI such as Soil 2 Lee an A-7-6 AASHTO class perform slightly better under rain-induced inundation conditions. This is in opposition to the criterion of limiting material PI as material selection criteria which is currently used by the NC state standard. This might at least cast doubt on the NCDOT material selection specification of limiting PI to 15% in the North Carolina coastal area. Providing suitable vegetation cover (to reduce infiltration and promote runoff) as well as drainage measures for the highway embankments could be very helpful to avoid detrimental effects of presence of water in the body of embankment.
