Influence of Geotextile and Geogrid Reinforcement on Strength Behaviour of Soft Silty Soil

Abstract

Roads are the most important component for the economic and social development of any country. India has a total road network of more than 6 million kilometers, which carry around 90% of passenger traffic and 65% of freight traffic. More than 20% land area of India is covered with soils having low California bearing ratio (CBR) and shear strength values. The pavement constructed over such soils will lead to rapid increase in construction and maintenance costs. This study presents a laboratory investigation about the combined effect of geotextile and geogrid reinforcement, placed in layers at various depths from top of specimen, on the strength behaviour of poor subgrade soil. Heavy compaction, soaked CBR and unconfined compressive strength (UCS) tests are conducted. The test results indicate significant improvement in CBR and UCS values for all geosynthetic reinforced cases, whereas ductility and rupture strength remains almost constant as compared to virgin soil. Scanning electron microscopy (SEM) analysis shows significant bonding between soil particles and fibers of geogrid, causing stress transfer from soil to reinforcing material and hence preventing soil from overstressing. It is concluded that combination of geogrid and geotextile can be used effectively for reinforcing poor subgrade soil.