Multiscale and Multifield Investigation on Soil Leakage at the Diaphragm Wall Opening During Excavation

Opening in diaphragm wall is a primary cause of water and sand leakage in excavation, often leading to severe excavation accidents. This process involves complex interactions between fluid flow, granular soil around openings, and continuum materials, yet there is a lack of appropriate calculation methods to address it. This study develops a multiscale, multifield calculation framework integrating the discrete element method (DEM), computational fluid dynamics (CFD), and finite difference method (FDM) to address the challenges of large deformation and fluid-soil interaction caused by through-wall leakage in excavation. A numerical model is developed based on a relevant case of retaining wall leakage, analyzing the effects of leakage depth, surcharge load, and water head. The study reveals that soil leakage at the diaphragm wall opening is driven by both geostress and fluid forces. As strain energy release from stress relief increases with leakage depth, it accelerates soil particle movement, resulting in greater soil loss at deeper levels. However, the soil arching effect at deeper levels limits the stress relief zone, reducing the influence area and mitigating the adverse effects of soil leakage. Additionally, while surcharge load behind the diaphragm wall has minimal impact on cumulative soil loss at the opening, it significantly increases ground settlement and wall deflection.