Clean and efficient slurry shield tunneling in sand and gravel ground: Clogging characteristics, mechanisms, and prevention measures

Clogging substantially increases energy consumption, reduces construction efficiency, and heightens safety risks in a slurry pressure balance tunnel boring machine (SPB TBM). This study investigates the characteristics and mechanisms of SPB TBM clogging in gravelly soil, explores the impact of clogging on energy consumption and construction efficiency, and proposes effective clogging prevention measures. A novel approach combining vibration signals with tunneling parameters is introduced to identify the clogging patterns and mechanisms in the slurry pipeline. The study found that clogging in the pipeline occurs in four stages, the vibration amplitude increased from 0.001 m/s² to 0.04 m/s², and the low-frequency vibration response in the 0–25 Hz range was significantly enhanced. Gravel accumulation forming an arch structure, which is the primary cause of clogging. Therefore, targeted measures, including flushing systems, additional slurry circulation mode, and the stone storage box, are proposed to address the clogging issue. Engineering practice shows that these measures reduced average energy consumption by 10–15 % and average TBM downtime due to clogging by 30–40 %, providing theoretical support and technical guidance for clean and efficient operations in similar tunnel construction projects.