Failure mechanisms and mitigation strategies of highway subgrade structures under rainwater erosion conditions

Rainwater erosion is widespread in China, particularly affecting subgrade stability due to complex geological formations and harsh climatic conditions. Sichuan, situated at the junction of the Tibetan Plateau and the Sichuan Basin, presents unique geological, climatic, and hydrogeological challenges that significantly impact highway operations and public safety. This study reviews the erosive geology of southeastern Sichuan, analyzes the mechanisms of highway subgrade damage, and identifies the primary forms and causes of hydraulic erosion-related degradation. Construction in water-prone areas often leads to subgrade settlement, foundation subsidence, slope collapse, damage to protective structures, and pavement cracking, all of which threaten road integrity. To address these hazards, this study introduces a novel subgrade structure. Using the Tianqiong Expressway as a case study, the effectiveness of this design in mitigating water erosion damage is evaluated. This structure not only prevents surface water infiltration into the subgrade but also promotes the rapid drainage of accumulated water. Consequently, this study provides valuable guidance for enhancing the durability and stability of subgrades, as well as practical insights for structural design in water-rich regions.