Utilization of synthetic reinforcement for enhancement of oil-contaminated subgrade soil in highway pavement

Oil-contaminated soil has a negative impact on the environment. Synthetic reinforcement of soil is used to improve the general quality of soil. Therefore, the main aim of this research is to investigate the effect of using of synthetic reinforcement for enhancement of oil-contaminated subgrade soil in highway pavement. Also, it aims to quantify the benefits of reinforcing the subgrade soil in pavement construction. The investigation was performed on two different types of soils. Moreover, four types of reinforcements (fiber, nonwoven geotextile, woven geotextile, and geogrid) were used for this study. Furthermore, the behavior of oil-contaminated soil to be used as a subgrade layer in pavement construction was also studied. The soil was contaminated with oil content from zero to 6% with respect to the dry soil weight to match the field conditions. The laboratory California bearing ratio (CBR) test was performed on unreinforced and reinforced natural and oil-contaminated soil. The optimum quantity of fibers and number of reinforcing layers were selected based on CBR values. The results indicated that CBR values increase with inclusion reinforcement. The optimum quantity of fibers which attains the highest CBR values depends on type of soil and percentage of oil content. The results showed that the soil contaminated with 2-3% oil content can be successfully used as a subgrade soil in pavement construction. Finally, the quantified benefits indicated that inclusion of two layers of reinforcement in height of specimen was sufficient to increase CBR values according to the type of soil and properties of reinforcement.