RESILIENT BEHAVIOUR OF REINFORCED SUBBASE MATERIAL

Abstract

Increase in the cost of aggregates and depletion of their sources make difficult to provide thicker granular layers. The new technological developments in non- metallic reinforcing materials have given rise to new high strength polymer materials like geogrids, geotextiles and geosynthetics. However, a very less amount of work has been done on reinforcing subbase granular materials. The granular materials subjected to repeated load undergoes both plastic and elastic deformations and magnitude of these deformations is a function of the number of load repetitions and many other factors. Primary cause of cracking of pavements has been attributed to the fatigue failure, resulting from repeated stress over a prolonged period of time. In the present study, resilient behaviour of reinforced granular subbase materialis investigated. Grading of the granular material was selected by the parallel curve technique using the MORTH-2001 specifications for GSB material. Netlon CE 131 and Tenax geogrids were used to reinforce the material and tests like CBR, Unconfined compressive strength and static triaxial tests were conducted. The CBR results indicated that the CBR value was highest, when the geogrid was placed at 100 mm from top of the specimen. The static triaxial tests were conducted at confining pressures of 0.4, 0.7 and 1.4 Kg /cm2 with varying positions of geogrids. The modulus of elasticity was found to have increased with confining pressure and with depth of geogrid. The maximum value of modulus of elasticity occurred when geogrid was placed at 16 cm from the top of specimen. The repeated triaxial tests were conducted with optimum position of geogrid and resilient modulus, recoverable strain, permanent strains were determined at various number of stress cycles, confining pressures and deviator stresses.