Research on muck conditioning for EPB shield tunnelling in composite formation

Area of Science:

• Geotechnical Engineering
• Tunneling Technology
• Material Science

Background:

• Earth pressure balance (EPB) shield tunnelling in composite formations presents significant muck conditioning challenges.
• High moisture content and complex strata ratios in formations like water-rich sand and argillaceous siltstone complicate excavation.
• Muck spewing accidents are frequent due to difficulties in optimizing muck conditioning schemes.

Purpose of the Study:

• To develop and optimize a muck conditioning scheme for EPB shield tunnelling in water-rich sand-argillaceous siltstone composite formations.
• To address challenges related to muck conditioning in complex geological conditions.
• To improve the efficiency and continuity of shield tunnelling operations.

Main Methods:

• Laboratory muck conditioning tests were performed on five different stratum ratios.
• Field tunnelling parameters (propulsion speed, penetration rate, thrust, torque) were analyzed.
• Dynamic optimization of muck conditioner ratios was conducted based on laboratory and field data.

Main Results:

• A specific muck conditioning scheme was established for varying ratios of water-rich sand and argillaceous siltstone.
• Optimal injection ratios for foam, bentonite slurry, CMC polymer, and mudstone dispersant solution were determined.
• Field data validated the effectiveness of the proposed laboratory-optimized conditioning scheme.

Conclusions:

• The developed muck conditioning scheme is effective for EPB shield tunnelling in water-rich sand-argillaceous siltstone composite formations.
• The optimized scheme helps mitigate muck spewing accidents and enhances tunnelling efficiency.
• The findings support the wider application of this conditioning strategy in similar geological conditions.