CBR Performance of Geosynthetic-Reinforced Granular Fills Over Expansive Soil Subgrades

Abstract

The performance of road pavements is closely linked to the durability of materials and the strength of the underlying subgrade. Constructing on weak subgrade soils can significantly increase costs and delay highway projects. The strength of a subgrade is commonly assessed through the California Bearing Ratio (CBR), defined as the ratio of the applied load to a standard load at a given penetration using a standard plunger. In India, flexible pavement design is primarily based on CBR values of subgrade soils. To improve weak subgrades, several stabilization methods are employed, with geosynthetics being among the most effective.
This study investigates the improvement in CBR strength of expansive silty clay soil reinforced with geotextiles placed at various depths within the CBR mould. Two different types of geotextiles were used to evaluate their effectiveness in enhancing soil strength. Further, the study focuses on reinforcing expansive soil with geogrid layers arranged in single, double, triple, and four-layer configurations at varying depths. Results indicate that incorporating geogrid layers consistently improves CBR values compared to unreinforced soil, with the degree of improvement depending on the number and placement of reinforcement layers.