During earth pressure balance (EPB) shield tunneling in clayey strata, issues such as clogging at the cutterhead and screw conveyor are common. The combination of foam and dispersant has been shown to effectively improve conditions and prevent these problems. This study focuses on the engineering project between Wenchu Station and Guanyin Station of Shenyang Metro Line 6. Initially, the types and concentrations of foam and dispersant were determined through performance tests. The effects of individual and composite conditioners were evaluated using four indicators: adhesion rate, fluidity, consistency, and shear strength. The optimal ratio of foam and dispersant was identified, and the appropriate ranges of each evaluation indicator were established. Additionally, the mechanisms by which dispersants condition clay were explored from a microscopic perspective. The results show that at a moisture content (MC) of 30%, the optimal performance with the composite conditioners is achieved when the dispersant injection ratio (DIR) is 10% and the foam agent injection ratio (FIR) ranges from 30%–60%. The following evaluation criteria are recommended for clayey strata: an adhesion rate below 0.3, consistency within 7–10 cm, fluidity within 14–16 cm, and shear strength under 20 kPa. The dispersan t creates distinct boundaries between clay particles, increases the thickness of the electrical double layer, and enhances repulsive forces. As DIR increases, the Zeta potential of the particles gradually decreases and stabilizes, whereas the total repulsive energy (VT/R) between particles continues to rise. This study offers practical guidance for conditioning EPB shield muck in clayey strata.
Li et al. (Wed,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: