Effectiveness of geotextiles in unsurfaced pavements over weak subgrade evaluated from accelerated field testing

Unsurfaced pavement sections are often constructed over weak subgrades and placement of geotextiles at the aggregate-subgrade interface has been shown to provide layer separation and pavement reinforcement benefits. As part of a recent full-scale pavement testing research effort at the University of Illinois, open-graded aggregate materials with large top-size particles were used to provide a "platform" for placement and compaction of dense-graded surface layers. Geotextile separation and reinforcement of the aggregate-subgrade interface was considered in the experimental design to improve load distribution within the aggregate layer and prevent material migration across the layer interface. A 305-mm thick foundation layer was first constructed over the subgrade, and was subsequently "capped" with a 152-mm thick surface layer comprising a dense-graded crushed limestone material. The test sections were loaded to failure under geotextile-reinforced and unreinforced conditions along two wheel paths separated by a distance of 2.4 m. The geotextile-reinforced sections performed significantly better and showed lower rate of rut accumulation compared to the unreinforced sections that underwent shear failure after a few load applications. The reinforced sections also sustained significantly higher number of load applications (up to 200% higher) before accumulating the same amount of rutting as the unreinforced sections. Excavation of transverse trench sections after testing showed significantly reduced interlayer material migration due to geotextile use.