Journal of Jilin Jianzhu University

Rock-soketed piles are the main foundation from of bridges in karst areas; the stability of underlying karst caves directly affects pile bearing safety, settlement control and long-term structural service performance. Focusing on the instability mechanism and stability of karst caves beneath rock-socketed piles, this study takes the karst caves under bridge pile foundations at Xinxing River Extra-Dose Bridge site of the GuangzhouKunming expressway reconstruction and expansion project as the engineering background. A finite element analysis model for cracking and instability of karst caves beneath pile toes is established using the extended finite element method, and a Abaqus-Python parametric analysis script is developed to realize automated modeling and batch calculation with variable parameters including cave size, position, shape, roof thickness, and loading conditions. The control variable method is adopted to quantitatively analyze the influences of roof thickness, piletop load, cave shape, and horizontal offset of the cave relative to the pile bottom on stability, and the instability mechanism and response of karst caves under increasing pile-end loads are systematically investigated. The results show that the instability failure of karst caves beneath pile toes undergoes four stages: compaction and stress redistribution, crack initiation and local yielding, crack propagation and plastic zone penetration, and overall instability and bearing capacity loss. The stability of karst caves is significantly improved with increasing roof thickness, while cave shape and load eccentricity exert considerable effects on cave stability. The research findings refine the stability analysis method for rock-socketed piles in karst regions and provide a theoretical basis and technical support for the design optimization and engineering safety assurance of bridge pile foundations in similar intensely karstified sites.