Strength Parameters of Kaolinite Clay Stabilized with Nano-Silica and Reinforced with Hemp Fibers under Freeze-Thaw Cycles: An Experimental Study

Freeze-thaw cycles (F-T cycles)  can significantly affect the geotechnical properties of soils. Therefore, in areas with high freeze-thaw potential, it is essential to consider the effects of these cycles during the durability and deformation analysis of slopes and excavations. One of the effective methods to improve the mechanical properties of clay soils subjected to F-T cycles is stabilization with nanoparticles and natural fibers. This study investigated the effects of F-T cycles on the strength properties of clay soils reinforced with nano-silica and hemp fibers. Experiments were conducted to determine the effect of nano-silica (SiO۲) and hemp fibers on the unconfined compressive strength (UCS) under F-T cycles. The soil specimens were treated with ۰.۵%, ۱%, and ۱.۵% nano-silica. Then, the samples were prepared with fiber-to-soil ratios of ۰.۲, ۰.۴, and ۰.۶ and the optimal dosage of nano-silica of ۱%. Next, they were subjected to ۱, ۳, ۵, and ۷, ۱۰ F-T cycles for durability testing. Finally, UCS tests were conducted to determine the strength of both reinforced and unreinforced samples. Based on the results of UCS tests, the optimum nano-silica content was ۱%, which increased the soil strength by ۹۲%. According to the UCS tests, when ۱% nano silica was used in soil, the maximum compressive strength was obtained, which is the criteria for optimum mechanical performance. The results of the UCS tests on the durability test samples under F-T cycles showed a decrease of ۲۷ to ۵۰% in UCS with the increasing number of cycles for the unreinforced samples. However, the combination of ۱% nano-silica and ۰.۴% hemp fibers resulted in a ۱۳% reduction in the UCS of the soil after ۱۰ freeze-thaw cycles, while strength was reduced by ۵۰% for the untreated soil. The interlocking zones and increased friction between the particles were improved by the usage of hemp fiber between the soil grains and nano silica. As a result, these phenomena effectively prevent excessive cracking during the application of F-T cycles, thereby enhancing the mechanical performance and durability of the samples.

کلیدواژه ها:

Kaolinite ، nano-silica ، Hemp fibers ، Freeze-thaw cycle ، Ground improvement ، Compressive strength