Detection and Prediction of Complete Destabilization in Shield Tunnel Slurries: Morphological Critical Thresholds Mediated by Organic Flocculant-Particle Interactions

The application of flocculants is a critical step in mud-water separation for slurry shield tunneling, where the selection of dosing parameters depends on a scientifically rigorous flocculation evaluation system. However, current evaluation systems suffer from ambiguous frameworks, redundant indicators, and a lack of quantitative analysis. To address these bottlenecks limiting the efficiency of mud-water separation, this study proposes the Complete Destabilization of Shield Slurry (CDSS) theory based on typical organic flocculants. Multiscale mud-water separation experiments and multistage particle edge image recognition technology (EMW) were employed to establish macroscopic mud-water criteria and deduce the morphological critical thresholds of slurry particles. Key findings include: (1) CDSS reactions achieve rapid flocculation, producing sludge with a solid content exceeding 40%, wastewater turbidity below 150 NTU, and negligible post-separation volume changes. (2) CDSS reaction probability exceeds 95% when the average particle size ≥ 0.22 mm and density distribution ≥ 5550 counts/dm². (3) CPAM demonstrates superior triggering efficiency (92%) compared to NPAM (66%) and APAM (18%), attributed to synergistic effects between electric double layer interactions (energy barrier < 185×10⁻⁹ J·m⁻¹) and bridging mechanisms. This study's flocculation framework optimizes mud-water separation and sets a new standard for slurry efficiency in engineering and environmental applications.