Abstract
To address critical challenges (unstable muck discharge, high blowout risk, and severe local wear) of Earth Pressure Balance (EPB) shield screw conveyors in water-rich sandy-cobble strata—where traditional single-phase simulations (pure Computational Fluid Dynamics [CFD] or Discrete Element Method [DEM]) fail to capture the intricate coupling between discrete cobbles and groundwater—a bidirectional CFD-DEM fluid-solid coupling model was developed, with the Beijing Metro New Airport Line project as the engineering prototype. Following the model development, numerical simulations were conducted under controlled earth pressure (504 kPa) and varied water-soil pressure ratios. Observations indicated that muck discharge remained stable when the water-soil pressure ratio ranged from 0.24 to 0.48; exceeding the critical threshold of 0.56 induced particle segregation and blowout, with the initial signal being reduced filling rate rather than immediate discharge surge, and dry muck efficiency dropping to only 22.4% of the theoretical value. An 80% reduction in total pressure was found to occur at the interface between the excavation chamber and screw conveyor within 80 seconds. Additionally, the screw conveyor exhibited a distinct “dual-peak, three-stage” wear distribution: an impact wear peak at the 0 m inlet and a frictional wear peak at 8.625 m. This is fundamentally distinct from traditional single-peak models, which fail to account for the differential impacts of particle kinetic energy attenuation and stage-dependent wear mechanisms throughout the conveyance process. Subsequently, a comprehensive analysis of flow field characteristics, particle kinematics, and wear mechanisms was carried out. Finally, further discussion was conducted pertaining to the engineering implications of the findings, providing direct technical support for the optimized design of screw conveyors (e.g., targeted structural reinforcement at key wear zones), the development of stratified anti-wear measures, and the configuration of a precise blowout early warning system with the critical water-soil pressure ratio (0.56) as the core monitoring indicator.
Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Acknowledgments
The authors acknowledge the financial support provided by the National Natural Science Foundation of China (Grant No. 52278385).
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National Natural Science Foundation of China,52278385.
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Caixia Guo* (Corresponding author): Supervision, Project Administration, Writing–Review & Editing, Funding Acquisition, Resources. Gang Liu: Methodology, Software, Validation, Visualization, Formal Analysis, Investigation, Writing–Original Draft. Xiaochan Wang: Project Administration, Resources, Funding Acquisition. Xinquan Zhang: Project Administration, Data Curation, Funding Acquisition. Xiuli Du: Project Administration, Resources. All authors have read and agreed to the published version of the manuscript.
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Guo, C., Liu, G., Wang, X. et al. CFD-DEM coupling analysis of EPB screw conveyor muck discharge in water-rich sandy cobble strata. Sci Rep (2026). https://doi.org/10.1038/s41598-026-41903-7
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DOI: https://doi.org/10.1038/s41598-026-41903-7
