Subgrade Stabilization Using Geogrids: Fid-Bau Portal

Subgrade Stabilization Using Geogrids

R. J. Clark / J. J. Hughes

This report summarizes the evaluation of geogrids used to stabilize soft subgrades under I-70 in Washington County in District 12-0. The project involved the reconstructed of 5 1/4 miles of plain cement concrete pavement on a four lane divided highway that ended at the West Virginia Border. During the removal of the existing pavement numerous areas of unstable subgrade were found. The District 12-0 geotechnical engineer proposed that geogrids be evaluated as an alternative subgrade stabilization method to reduce the amount of undercutting unstable subgrade and replacing this material with suitable material. The two geogrid materials (SS-1 and Miragrid) used in this study were manufactured by Tensar and Nicolon/Mirafi. During construction, plate bering tests were performed on the original subgrade and on the reinforced and replaced subgrade sections. Horizontal inclinometers were used to determine movement of the subgrade under construction equipment. Mays meter tests were performed on the completed pavement before opening to traffic and one year after completion to compare pavement smoothness. Based on the results of these tests and subsequent visual observations, it appears that both of these geogrid materials performed satisfactory over the various areas of soft subgrade since installation in 1989.