Freeze-thaw durability of fiber-lime-soil based on mechanical damage and crack features

Freeze-thaw cycling damages soil structure, leading to degradation of mechanical properties. A series of tests—including freeze-thaw cycling test, unconfined compressive strength (UCS), splitting tensile, computer tomography (CT), and scanning electron microscopy (SEM) tests—were conducted on lime-soil and fiber-lime-soil to investigate the degradation laws of mechanical properties and microstructural damage characteristics. Results demonstrated that the UCS, tensile strength, and peak strain of both lime-soil and fiber-lime-soil decreased in three distinct stages: a high-decline-rate stage, a low-decline-rate stage, and a stable-strength stage. Fiber-lime-soil exhibited superior mechanical performance compared to lime-soil. As the number of freeze-thaw cycles increased, the mean crack length, crack width and crack ratio of both soils increased. However, fiber-lime-soil showed fewer cracks and lower crack connectivity than lime-soil, indicating that fiber reinforcement enhanced crack resistance. Lime significantly improved soil strength, while fibers improved deformation resistance through interfacial forces and spatial-constraint effects between fibers and soil particles. The findings contribute to understanding the freeze-thaw resistance mechanisms of fiber reinforced soil, elucidating the relationship between strength deterioration and microstructural damage, and evaluating the freeze-thaw durability of such soils in seasonally frozen regions.