عنوان مقاله [English]
The waste tire is one of the fastest growing industries in the world, as recycling them have become one of the major challenges worldwide. Successful use of waste rubber as rubber-soil mixture (RSM) in improving the soil properties is ensured in a given geotechnical application when appropriately used. The present study provides an approach for the use of granular rubber as rubber-soil mixture layer in soil backfill. The behavior of soil alone and reinforced soil by one layer of RSM was investigated by standard CBR apparatus with load rate of 1.27 mm/min on samples. The rubber used in the RSM layer was granulated rubber, produced from waste tires. Four sizes of rubber particles of 1.26, 2, 2.83, 4.76 mm, four rubber contents of 2.5, 5, 7.5, and 10\% and three surcharges of 0, 2 and 4 kg were used. The provision of RSM layer might reduce the penetration of loading plate and increase CBR value. The results of the tests depict that the bearing capacity increases up to 75\% by using the optimum rubber content of 7.5\% in the RSM layer. Also the effect of RSM layer thickness of 1, 1.5, 2 and 3 cm on the behavior of sample was investigated. The results show that using the soil layer of 1.5 cm over RSM layer increases the bearing capacity of sample, especially for penetration of less than 5 mm. Overall; the results of tests demonstrate that the inclusion of waste granular rubber in soil with appropriate rubber size, rubber content and soil layer over RSM laye could improve the strength and deformation behavior of road beds substantially. On the basis of the study, the concept of using rubber-soil mixture layer not only improve the performance of shallow footings, embankment and road construction, but also, the environmental impacts of waste tires are attenuated by using as composite materials in civil works.