Effects of recycled polyethylene terephthalate fibers on strength behavior of cemented Babolsar sand

Construction of structures on sandy soils of northern part of Iran encounters problems due to lack of proper strength properties. In recent years, bottles of Polyethylene terephthalate (PET) such as water bottles caused an environmental threat due to their prolonged persistence. Utilization of these materials for soil improvement seems to be a sustainable approach. In this study, the effect of recycled PET on mechanical properties of Babolsar sandy soil is investigated through an experimental program using direct shear and consolidated drained (CD) triaxial compression tests. Various contents of PET were added to sand with 3%, 5% and 7% cement contents. Curing time and relative density of samples were 7 days and 70%, respectively. Results showed that addition of fiber improves strength parameters such as cohesion and internal friction angle. Furthermore, the effect of the fiber is less marked with an increase in cement content. The samples with 3% cement demonstrated better results in both direct shear and tiaxial tests. By adding 0.5% and 1% PET fibers to the samples containing 3% cement at 100 kPa pressure, the ratio of strength in direct shear tests increased 13% and 24%, respectively, and in the triaxial test, it increased 50% and 93%, respectively.