Investigating the use of palm tree pruning waste (PTPW) as an alternative to geotextile in reinforcing highway subgrade under repeated loads

In this study, several experiments were conducted on the subgrade used in the design of highways, focusing on providing two-way benefits for the environment both by recycling a waste material and improving the rutting performance of the sand subgrade under cyclic traffic loads. In this context, a series of laboratory experiments were conducted to compare the performance of commercially produced geotextile and palm tree pruning waste (PTPW) as soil improvement agents. The experimental results of the study were evaluated in terms of permanent (plastic), total and elastic deformation, rutting depth reduction (RDR), traffic benefit ratio (TBR), elastic deformation percentage. According to the experimental results, the sand subgrade reinforced with geotextile and PTPW performed well in terms of permanent and elastic deformations compared to the unreinforced condition. It has also been found that the most satisfactory performance is achieved when the geotextile or PTPW is placed at both an burial depth of 50 mm and 100 mm. In this case, the TBR values of geotextile and PTPW reinforced subgrades are almost the same at 20 mm of permanent deformation. In addition, when the results are evaluated according to RDR, it is seen that the rutting depth of geotextile and PTPW reinforcements decreased by 49.31% and 37.15%, respectively, at the end of 5000 load cycles.