EFFECT OF GEOGRID & BAMBOO – GRID REINFORCEMENT IN SOIL SUBGRADE USING STATIC & DYNAMIC CONE PENETRATION TEST

Abstract

Weak and soft subgrade soils often cause excessive settlement, rutting, deformation, and premature pavement failure under repeated traffic loading. Enhancing engineering properties of such soil is therefore essential to improve effectiveness and long-term durability of pavement system. Among various ground improvement techniques, the use of geosynthetic and natural reinforcement materials has emerged as a reliable and eco-friendly method for improving soil strength and enhancing its load-carrying capacity. A comparative evaluation of sandy soft subgrade soil with geogrid and bamboo grid was carried out using SCPT and DCPT. Laboratory investigations were performed on unreinforced and reinforced soil sections by placing geogrid and bamboo-grid layers at depths of 50 and 100 mm inside the developed soil bed. Experiments were conducted to evaluate the improvement in penetration behavior, soil stiffness, cone resistance and overall performance of the reinforced soil subjected to loading. The experimental findings indicate that both reinforcement materials significantly improved the behavior of the soft subgrade in comparison to the untreated soil. The penetration depth was reduced , while cone resistance and stiffness were enhanced in the reinforced soil sections. In the SCPT analysis, at 50 mm penetration depth, the geogrid-reinforced soil exhibited an increase of about 225% in cone resistance, while the bamboo-grid reinforced soil showed nearly 232.87% improvement in cone resistance compared to the unreinforced soil. Similarly, at 100 mm penetration depth, the geogrid reinforcement showed an increase of about 61.36% in cone resistance, whereas the bamboo-grid reinforcement achieved nearly 90.05% improvement compared to the unreinforced soil. Similarly, the DCPT results demonstrated substantial enhancement in penetration resistance, with improvements reaching approximately 300% at 50 mm reinforcement depth. At 100 mm depth, geogrid and bamboo-grid reinforcement achieved nearly 200% and 202.87% improvement, respectively. The study concludes that geogrid and bamboo-grid reinforcement techniques effectively improve bearing capacity & overall behaviour of soft subgrade soil. Moreover, bamboo-grid reinforcement can serve as an economical, eco-friendly, and locally available alternative to conventional reinforcement materials for sustainable pavement and geotechnical engineering applications.