Drained Triaxial Response of Natural Clay Reinforced with Natural Hemp Fibers

Abstract Reinforcement of soils with fibers generally increases the mechanical properties of the fiber-reinforced soil (FRS) system. However, published literature is limited to investigating the undrained response of clay and synthetic fibers, with few studies targeting natural clay and natural fibers under drained conditions. There is a need to study the response of fiber-reinforced clay systems under drained conditions to assess long-term stability. This paper investigated the drained shear strength and durability of clays reinforced with natural hemp fibers using isotropically consolidated drained triaxial tests, in which the fiber content, confining pressure, and compaction water content were varied. Results showed that the incorporation of hemp fibers improved the deviatoric stress at failure by up to 60%, which increased the drained cohesion and friction angle of the FRS by 7–10 kPa and 3–7°, respectively. The increase in cohesive intercept was not affected by the compaction water content, while the increase in friction angle was pronounced in specimens compacted at optimum water content (w = 18%). Durability tests showed that the improvement in strength due to hemp fibers diminishes after 3 weeks of curing prior to drained testing, indicating the dramatic negative impact of degradation of natural fibers on the mechanical performance of fiber-reinforced clay and the need for industrial treatment of the fiber.