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This study explores the mechanical properties and synergistic mechanisms of silty sand modified with guar gum (GG) and polypropylene fiber (PP fiber) through a series of unconfined compressive strength (UCS) tests, direct shear tests, and direct tensile tests. The test results reveal that the unconfined compressive strength (UCS) of silty sand can be dramatically improved by incorporating GG, boosting its strength by up to 23 times compared to the natural soil. Adding PP fiber further enhances the UCS and effectively mitigates brittle failure. GG dominates the increase in shear strength by enhancing cohesion, while the PP fiber optimises the shear stability by increasing the internal friction angle. The shear strength of the GG-PP fiber-enhanced soil can be boosted by 235% compared to natural soil. The synergistic effect of GG and PP fibers enables the tensile strength of the improved silty sand to reach 122.75 kPa, representing a 34.15% increase compared to soil with only GG incorporated. However, if the fiber content is too high (> 0.5%), the tensile strength will decrease due to increased porosity. The study found that GG enhances the cohesion between soil particles through hydrated gel, and the PP fiber inhibits crack propagation and improves ductility through the bridging effect. The two form a bonding-bridging synergistic system, which significantly optimises the mechanical properties of the soil. This combined improvement scheme has both high strength and high ductility and can replace traditional inorganic cementitious materials, providing new ideas and methods for the application of silty sand in roadbed engineering, slope reinforcement, and other fields.

来源平台：GEOTECHNICAL AND GEOLOGICAL ENGINEERING