Permanent Strain of Randomly Oriented Fiber Reinforced Rural Road Subgrade Soil under Repetitive Triaxial Loading

Series of repeated load isotropic triaxial compression tests were carried out on rural road subgrade material (with and without fiber reinforcement) under unconsolidated undrained conditions to study the accumulation of permanent strains with loading cycles. Influence of number of loading cycles, deviatoric and confining stress levels, and fiber reinforcement on the accumulated permanent strains of subgrade material were studied. Tests were conducted on reconstituted local Roorkee clayey soil samples, which were reinforced with randomly distributed fibers (coir and polypropylene) at optimum content. Test results were analyzed to address the influence of above said variables and were compared with the un-reinforced one. It is observed that permanent strain behavior decreases with increase in confining pressure but increases with increase in the number of load cycles and cyclic deviatoric stress application. The reinforcement effect (resistance to permanent deformation) is found to increase appreciably when mixed with clayey soil. Coir fiber showed a higher resistance than polypropylene fiber. With the above mentioned finding it may be concluded that coir fiber can be used effectively in rural road subgrade.