Behavior of a Subgrade Soil Reinforced by Waste Tire Textile Fibers under Static and Cyclic Loading

Owing to the soaring environmental threats ensued by the ever-increasing quantities of end-of-life tires (ELTs) across the globe, today the issue of recycling and reusing these waste materials is being discussed by scientists of various fields more than ever. As a main industrial and scientific area, civil engineering is a consumer of new and waste materials and experts are striving to introduce new and sustainable ways of reusing ELTs as construction material. In this study, a series of static and cyclic laboratory tests were performed to contribute to managing and preventing the burial of a part of hazardous wastes produced during the recycling process of worn tires. Compaction, direct shear, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and repeated load triaxial (RLT) tests under various stress levels were conducted after the addition of different contents of waste tire textile fibers (WTTFs) to a sandy soil. Fiber inclusion enhances all geotechnical properties of the soil under static state. Under dynamic state, especially when employed to reinforce the subgrade of a road, these fibers can increase the energy absorption and dissipation properties of the soil, as well as increasing the resilient modulus and damping ratio with an optimum fiber content of 1%-2%. An energy-absorbing layer could be established by using the fibers. A new model is also presented to accurately predict the resilient modulus of the reinforced soils. Moreover, the model is adapted for unreinforced soil and compared against some relatively precise models in the literature. The proposed model yields totally satisfactory results.