Design and Economic Analysis of a Flexible Pavement on a Geosynthetic Reinforced Subgrade

This study investigated the effect of geogrid reinforcement on the mechanical property of an unsuitable road soil with respect to appropriate placement in the pavement structure and implication on the cost of the development of the road. Sample was collected from the stockpile of an unsuitable soil material at a bridge site and subjected to identification, geotechnical strength (CBR) and chemical stabilization tests. CBR strength evaluation test was further performed on the soil sample when reinforced with the use of a geosynthetic, triaxial geogrid (Tx 160). A flexible pavement structure was designed for low, medium and heavy traffic level using three design methods with the improved soil subgrade. The corresponding relative cost advantages were also determined using the pavement thickness reduction factor. The results established the geogrid reinforcement is a better alternative to chemical stabilization of an unsuitable AASHTO A-4 soil. The design results denoted a significant pavement thickness reduction factor as a result of geogrid reinforcement within 13% - 67% savings in pavement thickness for all the pavement design methods employed. The use of geogrids should, therefore, be encouraged as an economic form of improving subgrade soils for pavement works.