Tests and analysis of geogrids as base-reinforcing materials

Abstract

A quantitative assessment of geogrids as base reinforcing material in paved roads is clearly necessary when a design is needed and decisions are to be made as a consequence. Two full scale single wheel load tests were conducted to determine the performance of geogrids as base reinforcing materials in paved roads. These two full scale tests were set up with different base thicknesses, material properties, loading conditions and geogrids. Load, speed, and direction of a test cart were controlled with a computer. Although many types of instruments were installed, measurements of vertical deformation of the pavement surface proved to be the most useful. The Traffic Benefit Ratio (TBR), defined as the ratio of the life of a reinforced section to the life of a similar unreinforced section, was used as a primary design parameter. Comparisons between reinforced and unreinforced bases are presented. The parameters used for comparison were permanent vertical deformation, number of repetitions to failure, tire load, and thickness of base course. Test results showed that the maximum TBR for a Tensar BR2 geogrid was 10. This TBR was obtained at a design deformation of 1.0 inch with 2 inches of asphalt over 10 inches of base over a CBR 3 clay subgrade. TBR's for other conditions ranged between 1 and 10. A design reference chart is presented for using Tensar BR1 and BR2 Geogrids.