Project Details

NCDOT routinely and successfully stabilizes subgrades of pavements constructed west of Interstate-95. The depth of the stabilized subgrade has been typically limited to 178 mm (7 in.) or 200 mm (8 in.) depending on whether cement or lime stabilization is needed. The subgrade stabilization practices has resulted in excellent, uniform, and cost effective subgrade support. With the recent advances in earthwork equipment, new cost competitive equipment is capable of performing deep subgrade stabilization to approximately double the current thickness, e.g. to about 406 mm (16 in.). This research project investigated the potential pavement performance improvement of deep layers of subgrade stabilization (to about 406 mm) compared to the current NCDOT subgrade stabilization practice (up to 200 mm). The motivation is to maximize the benefits of deep layers of subgrade stabilization, by quantifying the potential performance improvement of deeper subgrade stabilization over the current NCDOT practice. Performance improvements of deep layers of subgrade stabilization were evaluated using data collected at a test site of lime and cement stabilized sections constructed for this study. The test sections are laid out starting with the first control section, followed by 2 deep layers of subgrade stabilization and ending with the second control test section. The control test sections were designed and constructed to the current NCDOT practice, while deep layers of subgrade stabilization are composed of chemically stabilized layers approximately 1.5 and 2 times the stabilized depth of the current NCDOT practice. Dynamic Cone Penetrometer (DCP) and Falling Weight Deflectometer (FWD) data were collected at the site and used to evaluate the performance improvement from the deep layers of subgrade stabilization sections. Results from this study suggest that using deep layers of subgrade stabilization will result in improved performance and also could be cost effective given the decreased thickness of the asphalt pavement layer as well as in terms of life-cycle cost given the potential of a longer pavement life.