<p><p><figure id='attachment_3447' style='max-width:696px' class='caption aligncenter'><img class="wp-image-3447 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph showing rutting in an asphalt pavement with a geosynthetic separation layer." width="696" height="525" /><figcaption class='caption-text'> Al-Qadi and Appea (2003)</figcaption></figure></p><p><h2>Project Summary/Scope:</h2>The research was conducted on the secondary road pavement section built in Bedford County, Virginia, as a part of the realignment of Routes 616 and 757. A 150-meter long pavement section consisting of nine individual segments, each of approximately 15 meters in length was studied. Three sections were stabilized with geotextiles, three with geogrids, and remaining three were control sections.</p><p>Subsurface Conditions: Base course material was limestone of VDOT gradation 21-B. Subgrade CBR was 6% and 10% at in situ moisture-density values. Limestone of VDOT gradation 21-B was used for base course construction. Base course thicknesses were 100, 150, and 200 mm. A 95-mm thick hot mix asphalt layer was placed on the base course of each section.<br><h2>Performance Monitoring:</h2>A layered elastic analysis software and KENLAYER software were used to calculate the vertical stresses under the HMA layer which were used with FWD deflections to predict rutting rates with a mechanistic equation including the separation function of the geotextiles. Results of Surface Curvature Index (SCI) and Base Damage Index (BDI) for all nine sections collected during an eight-year period were analyzed and corrected to a standard temperature of 20°C. MODULUS Version 5.0 and ELMOD programs were used for FWD data analysis. The temperature correction model was developed from statistical analysis of measured deflections and HMA mid-depth temperatures and was applied to the study. The thickness of HMA used on the temperature correction model was obtained by direct measurement of the thickness of the HMA through field cores. Back calculation analysis for elastic modulus did not provide a unique solution.</p><p>Control sections had greatest amount of rutting and Base Damage Index (BDI) followed by geogrid-stabilized sections and geotextile-stabilized sections. Geosynthetically-stabilized sections significantly improved the performance of 100-mm thick base course sections.<br><h2>Project Technical Paper:</h2>Al-Qadi, I.L. and Appea, A.K. (2003). “Eight-year of field performance of a secondary road incorporating geosynthetics at the subgrade-base interface.” <em>Transportation Research Record No. 1849</em>, pp. 212-220.<br><h2>Date Case History Prepared:</h2>November 2012</p></p>