The Influence of Flocculant Type and Molecular Weight on the Dehydration Efficiency of Shield Slurry and Research on the Settlement Mode

Abstract

With the acceleration of urbanization in China, the slurry balance shield method is increasingly used in tunnel engineering, generating large amounts of high-moisture-content shield slurry that poses serious environmental threats. Dewatering is a key step for resource utilization of this slurry. This study systematically investigates the effects of different types (APAM, CPAM), molecular weights (8 million, 12 million, 16 million), and concentrations (0.1%–0.3%) of flocculants on the dewatering efficiency of silty clay shield slurry from the Changchun Metro Airport Line. Settlement experiments were conducted to analyze changes in sediment height and moisture content. Results show that anionic polyacrylamide (APAM) with a molecular weight of 16 million and concentration of 0.1% (Group A161) achieved the best dewatering performance. Additionally, a double-exponential decay model (R² > 0.99) was established for sediment height and equivalent moisture content over time, providing a reliable theoretical basis and prediction tool for practical flocculation dewatering processes.