effects of recycled polyethylene terephthalate fibers on strength behavior of cemented babolsar sand

Sandy soils constitute a large part of the soils of the northern part of iran. the construction of structures on these soils will have some problems due to a lack of proper strength properties. on the other hand, in recent years, bottles of polyethylene terephthalate (pet) plastics, such as water and soda bottles, have led to the emergence of an environmental threat due to their prolonged durability in the environment. the utilization of these materials for soil improvement seems to be a sustainable approach. in this research, the effect of recycled pet on the mechanical properties of babolsar sandy soil is investigated through an extensive experimental analysis carried out using direct shear and consolidated drained (cd) triaxial compression tests. various concentrations of pet were mixed to sand with 3%, 5%, and 7% cement contents. the curing time and relative density of samples were 7 days and 70%, respectively. the results showed that the addition of this fiber improved strength parameters such as cohesion and internal friction angle. furthermore, the effect of the fiber was not significant with an increase in cement content in samples. the samples with 3% cement showed better results in both direct shear and triaxial 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 by 13% and 24%, respectively, and increased in the triaxial test by 50% and 93%, respectively.