Study on stress-strain performance and support mechanism of flexible surface soil nail wall

To address the engineering safety challenges in flexible surface soil nail wall support systems, this study investigates the support mechanisms of such structures through a case study of foundation pit support engineering for the Tumor Diagnosis and Treatment Center at the First People's Hospital of Aksu Prefecture. Utilizing particle discrete element method, a three-dimensional numerical model was developed to simulate the entire construction process of flexible surface soil nail walls. The model conducted numerical simulations for excavation, drilling, grouting, and mesh installation stages under layered excavation modes, with particular focus on particle displacement, structural stress, local characteristics of flexible surfaces and soil nails, and support mechanisms. Results demonstrate that central soil nails experience maximum axial stress while upper and lower sections bear relatively lower loads. Horizontal displacement shows rapid changes during the initial week but stabilizes after 20 days. Cumulative settlement exhibits significant fluctuations in the first 10 days before stabilizing post-20-day period. During construction, soil displacement progressively increases in the foundation pit. Stress redistribution occurs due to excavation and flexible surface support, resulting in wavy displacement curves. Central soil nails experience greater tensile forces than their ends, forming convex stress-strain curves. Leveraging the discrete element method's core advantage of directly simulating particle motion and contact interactions, this study overcomes the limitations of traditional finite element methods in simplifying soil discrete nature. The research provides unique guidance for support design optimization, construction risk control, and performance evaluation through multi-scale correlation analysis spanning microscopic mechanisms, mesoscopic evolution, and macroscopic responses in soil nail wall support engineering.