Performance Behavior of Geogrids at Interface of Ballast and Granular Soil

Abstract

The use of geosynthetics in civil engineering projects is very common these days. The role of geogrids in stress distribution and reducing displacement is undebatable, and most of the civil engineering projects have been benefitted by the use of such products. The construction of railway embankments for heavy axle loads and high speeds is a big challenge with increasing population and demand for better economic solutions. The appropriate determination of the value of force required for pulling out the geogrid from the soil is of significant importance for reinforced soil structures. In this paper, efforts are made to understand the field behavior of geogrids under heavy loading. Therefore, pullout tests simulating the reinforced railway embankments under heavy axle loads were conducted in the laboratory. A total of 36 numbers of pullout tests were conducted in the large experimental box on biaxial and triaxial geogrids to study their behavior when used for railway embankments. The tests were conducted at two different strain rates of 5 mm/min and 1 mm/min for understanding the varying effects of strain rate under high stress. Results indicate that the biaxial geogrids serve a better alternative for railway applications under high stresses. The biaxial geogrids provide 33.51% higher pullout resistance and 59.28% more elongation (for the stress of 250 kN/m2) as compared to triaxial geogrid. This study also concludes that both triaxial and biaxial geogrids behave as a strain-hardening material, with biaxial geogrid showing more effect of hardening. Under the low strain rate of 1 mm/min, the biaxial geogrid performs better than triaxial geogrid for the whole load range adopted for the experiment. However, under a higher strain rate of 5 mm/min, the biaxial geogrid underperforms after the stress value of 50 kN/m2.