Experimental investigation of the mechanical behavior and engineering properties of sand reinforced with hemp fiber

Tensile components are present in soil-based fibers that are dispersed randomly and are used to support tensile stress. The stabilization and shear strength of soil is increased through the application of fiber reinforcement, which imitates the reaction of tree roots. Human has used reinforced soil for the construction of various structures for a long time. Today, soil reinforcement is an effective and reliable means of increasing the strength and stability of soil masses. Previous studies were mainly focused on the behavior of soils reinforced with synthetic fibers and few studies were conducted on soils reinforced with natural fibers. Since natural fibers are abundant in nature, they seem to be economic options if their behavior can be stabilized. The present study investigated the behavior of soil reinforced with hemp fibers. Several static triaxial tests were carried out in this research to assess the resistive behavior of Babolsar sand reinforced with randomly distributed hemp fibers. Hemp fibers were mixed into the soil in amounts of 0.3, 0.6, and 0.9% by dry weight and with lengths of 6, 10, and 14 mm. Static triaxial tests were performed at confining pressure of 50, 100, and 200 kPa. Test results indicated that there was a considerable effect on the behavior of sand due to the presence of fibers. Moreover, the results of the examinations of hemp-reinforced sand revealed that fibers improved the shear strength parameters, peak strength, yield strain, and stiffness of the sand. Regarding the outcomes, adding 6 mm fibers to soil results in increases in peak strength ranging from 331% in the greatest condition (fiber weight ratio of 0.9% and 50 kPa confining pressure) to 21% in the lowest state (fiber weight ratio of 0.3% and 200 kPa confining pressure). The maximum and minimum strength increase ratios for 10 mm and 14 mm fibers occur under the same circumstances as for 6 mm fibers. Thus, the highest and minimum strength gains for 10 mm fibers are 499% and 39%, respectively. For 14 mm long fiber, these figures are 845% and 49%, respectively. It is worth mentioning that the internal friction angle in the case of unreinforced soil is equal to 43°. This value is equal to 49° for reinforced soil containing 0.3% of fiber with a length of 6 mm and in most cases reaches 57° for reinforced soil containing 0.9% of fiber with a length of 10 mm. The amount of cohesion of reinforced soil containing 0.3% of fiber with a length of 6 mm is equal to 65 kPa and in most