Residual wheat straw reinforcement for resilient cohesive soils against coupled cyclic wet-dry environment and seismic shaking

Abstract This study examined the potential of wheat straw fibers (WSF), a globally abundant agricultural waste, to mitigate the combined effects of wetting–drying (W-D) cycles and seismic shaking on cohesive soils using a model study. WSF was mixed into the soil at varying percentages. Subsequently, these specimens were subjected to repeated W-D cycles, and their progress was methodically recorded using cinematography. The results demonstrated that W-D cycles significantly increased desiccation cracking in untreated soils. Incorporation of WSF substantially mitigated crack propagation by enhancing tensile strength and promoting more uniform stress distribution within the soil matrix. Higher WSF content further improved soil resilience, particularly under fluctuating moisture conditions. Seismic loading reduced the relative crack surface area and crack density but increased crack length, with post-seismic W-D cycles exacerbating cracking. WSF effectively reduced these parameters in an approximately linear manner up to 0.8% content. Mechanical performance, measured through cone index (CI) value, improved with W-D cycles due to cyclic moisture-induced shrinkage, and WSF-treated soils exhibited higher CI values than untreated specimens, even after seismic event (SE). Similarly, WSF reduced volumetric deformations, including swell-shrinkage, induced by both moisture cycling and seismic effects, highlighting its role in maintaining soil integrity under dynamic conditions. Comparative analysis shows that although WSF performs slightly lower than conventional polypropylene fiber (PF) for crack resilience and strength stabilization under coupled W-D environment and SE, it is a more sustainable choice, emitting 91% less CO 2 and embedding 93% less energy than PF for a 1 km two-lane road project at an equivalent dosage.