Effect of Geogrid Reinforcement on Shear Strength Characteristics of a Rubber-Sand Mixture under Undrained Triaxial Test

Utilization of rubber-sand mixtures as construction materials, such as lightweight filling materials, embankment construction, seismic isolation materials, … etc., provides significant advantages, as scrap tires induce environmental issues. In this study, unconsolidated undrained triaxial tests were performed to examine the shear-strength characteristics of geogrid-reinforced sand-rubber mixtures. The rubber percent (10%, 20%, 30%, 40%, 50% and 60%), the confining pressure of the cell (19.6 kPa, 49 kPa and 98 kPa) and the number of geogrid reinforcements (1 to 4) were varied for investigating the impact of these parameters. The relative density of sand remained constant (80%) during the test. The test results were evaluated in terms of the stress-strain characteristics of rubber-sand mixtures. The test findings demonstrated that by increasing the confining pressure of the cell, the same rubber-sand mixtures with the same relative density and rubber content take more loads. The peak stress of unreinforced rubber-sand mixtures increased with the increasing proportion of rubber content up to 30%, beyond which it decreased as rubber content increased. Maximum peak stress and axial strain have been achieved with 50% of the rubber content and four layers of geogrid reinforcement. The brittleness index of the rubber-sand mixture reduces when geogrid reinforcement is added. The minimum brittleness was found to be 0.042 at 50% rubber content with three layers of geogrid reinforcement. KEYWORDS: Geogrid, Shear strength, Triaxial test, Rubber-sand mixture, Soil reinforcement.