Tunneling Clay Dispersant — Chemi Tech Professional Solution

During shield tunneling in clay strata, mud cakes often form on the cutterhead and screw conveyor, drastically reducing advance speed and accelerating equipment wear. Traditional remedies—adding more water or frequent manual cleaning—are costly and can risk groundwater ingress or soil loss. Chemi Tech introduces a specialized clay dispersant that chemically breaks down the high plasticity and strong cohesion of clay minerals. 

1. Pain Points & Demand 

Clay particles in water tend to compress the electrical double layer, causing attractive forces to dominate and forming dense agglomerates. These agglomerates stick to cutterhead openings, mixing arms, and chamber walls, creating tough mud cakes. Once formed, excavated soil cannot discharge smoothly, torque spikes, and in severe cases, the chamber must be opened manually. The market urgently needs a dispersant that interrupts clay agglomeration at the source, rather than relying on mere physical dilution.

2. Product Mechanism 

Chemi Tech clay dispersant is a high-molecular-weight compound blending anionic polymers and inorganic electrolytes. Its action proceeds in two steps: first, anionic groups neutralize the electrostatic charge on clay edges, reducing van der Waals attraction; second, polymer chains extend from the particle surface, forming a steric barrier that prevents re-agglomeration. The dispersion remains stable even under high shear.

3. Application Procedure 

Step 1 – Pre-conditioning: Prior to shield launch, pre-dissolve Chemi Tech dispersant into the circulation water tank at a ratio of 0.3%–0.5% by weight. Stir until fully dissolved. 

Step 2 – Injection method: Once chamber pressure is stable, inject the dispersant solution at 10–15 liters per minute through ports on the cutterhead center or chamber bulkhead. Adjust the injection rate based on the real-time condition of excavated soil; the key is to ensure full contact between dispersant and clay. 

Step 3 – Monitoring: Record cutterhead torque, screw conveyor speed, and muck temperature after each ring advance. A torque drop exceeding 15% indicates effective dispersion. If muck still contains lumps larger than 5 mm, increase the injection rate. 

Step 4 – Adjustment: For high-plasticity clay (PI > 30), raise the concentration to 0.8% and apply short intermittent advance intervals, allowing the dispersant to react inside the chamber for 5 minutes.

4. Case Study 

A metro project in a city encountered full-face clay ground. Original advance rate was only 6 mm/min, with cutterhead torque reaching 90% of rated capacity. After applying Chemi Tech dispersant per the above procedure, torque stabilized at 55% rated value by the third ring, and muck changed from pasty massive lumps to uniform grains of 1–2 cm. Subsequent advance rate rose to 14 mm/min, and daily progress increased from 4 to 9 rings. No chamber blockage occurred during the entire section.

5. Summary 

Chemi Tech clay dispersant directly targets the root cause of clay agglomeration through precise chemical design, significantly reducing tunneling resistance in clay strata. Combined with scientific injection parameters and real-time monitoring, it enables continuous, high-efficiency, low-risk excavation. For a tailored solution and field trial guidance, contact the Chemi Tech technical team.