Laboratory Evaluation of polypropylene fibers and nano-SiO2 on geotechnical properties of clayey soils

Improvement of problematic soils, as an inevitable issue, has an important role in the construction projects. Adding some additive materials to the soil, has been considered as one of the effective procedure in improving characteristics behavior of soils. In this study, the effect of polypropylene fibers and nano-SiO2 in combination with clay was investigated, as a novel method, in order to refining mechanical properties of the soil. The purpose of this research is to investigate the effect of nano-SiO2 and polypropylene fibers on the properties of low plasticity clay by applying Unconfined Compression Test. Three different mixtures of the proportion of polypropylene fibers(0.25 %, 0.5%, and 1% of dry weight of clayey soil) and nano-SiO2 (0.5%, 0.75%, and 1% of dry weight of clayey soil) has been used. The results of this study show that adding the mixture of polypropylene fibers and nano-SiO2 into the clay soils, leads to 4.69% and 4.17% increment of unconfined compressive strength and modulus of elasticity, respectively, in comparison to the untreated clay. Also adding nano-SiO2 to the soil, causes more failure of samples occur respect to the case in in which the soil is getting mixed with fiber, though by increasing the amount of fibers, the failure mechanism of refined samples changes, thus the failure strain increases.