Damage evolution and hydro-mechanical degradation of basalt-fiber-reinforced compacted clay under drying–wetting cycles

The structural, hydraulic, and mechanical responses of fiber-reinforced compacted clay under drying–wetting cycles directly affect the long-term structural integrity and failure risk of geotechnical structures, yet their interrelated evolution at different fiber contents remains unclear. To address this issue, compacted clay specimens with basalt fiber (BF) contents of 0, 0.2%, 0.4%, and 0.6% were subjected to up to 12 drying–wetting cycles. Surface cracking, hydraulic conductivity, and triaxial strength parameters were quantitatively characterized at prescribed cycle numbers. The results showed that drying–wetting cycles promoted crack initiation, propagation, and reorganization. BF transformed large, concentrated major cracks into finer, more dispersed cracks while suppressing the increase in hydraulic conductivity and strength degradation. Crack evolution occurred mainly during the first four cycles. From cycles 6 to 12, the surface crack ratio increased by only 0.19–1.00 percentage points, whereas hydraulic conductivity continued to increase by 16.6–86.7% and peak deviator stress continued to decrease, indicating that surface crack evolution and hydraulic–mechanical degradation were asynchronous. After 12 cycles, specimens containing 0.6% BF exhibited a 44.7% lower surface crack ratio and a 99.5% lower hydraulic conductivity than unreinforced clay, while their peak deviator stress was up to 53.2% higher at a confining pressure of 100 kPa. The mechanical reinforcement provided by BF was mainly attributable to the enhancement and retention of cohesion. These findings provide a basis for damage-resistant material design and long-term failure risk assessment of impervious liners, dam cores, and embankment fills exposed to alternating wet and dry conditions.