Shield Tunneling Clay Dispersant Solution: Tackling Mud Cake and Cutterhead Sticking

During shield tunneling, high-plasticity clay strata often cause mud cakes to wrap around the cutterhead and hinder soil flow inside the chamber. This leads to elevated torque, increased thrust, screw conveyor blockages and poor muck discharge. In severe cases, manual cleaning is required, with single-event costs reaching hundreds of thousands of yuan. Chemi Tech has years of experience in ground conditioning and has developed a specialized dispersant to tackle the clay agglomeration challenge at the molecular level.

Market pain points concentrate in two areas. First, the cutterhead zone. Clay particles dehydrate and harden under heat and pressure at the cutterhead openings, forming a dense mud cake that acts like a concrete coat, reducing penetration rate. Second, the chamber interior. Clay particles attract each other to build a 3D network, turning the soil into a gel-like mass that cannot be discharged. Traditional methods like simple water dilution or generic dispersants provide only temporary relief, and excessive water often triggers spewing risks.

Chemi Tech's shield tunneling clay dispersant follows the principle of "intercalation and deconstruction." The polymer chains carry abundant negative charges that insert between clay mineral layers. Electrostatic repulsion forces the layers apart, while the polymers coat particle surfaces, blocking van der Waals attraction. Lab rheometer tests and field cross-validations show that at a dosage of 0.1%-0.3% by muck weight, the plasticity index drops by 30%-50%, and mud cake hardness reduces to a level that can be manually peeled off with ease.

The application procedure comprises four steps. Step 1: On-site testing. Collect in-situ clay samples and measure basic rheological parameters such as liquid/plastic limits, zeta potential and shear strength. Step 2: Formula matching. Based on test results, determine the dispersant dilution ratio and addition rate. Step 3: Injection execution. Inject the dispersant solution through foam ports ahead of the cutterhead or via bulkhead access points, using continuous or intermittent mode with injection pressure controlled at 0.2-0.5 MPa. Step 4: Dynamic monitoring. Use earth pressure sensors and torque meters for real-time feedback. When torque drops by 15%-20% and chamber pressure fluctuation stays below 0.05 bar, the dispersion effect is considered satisfactory.

A field case confirms this approach. During a metro shield drive through full-section hard plastic clay, torque climbed to 3800 kN·m and thrust to 28,000 kN by ring 27, with muck discharge only at 60% of normal rate. After applying Chemi Tech dispersant at 0.15% dosage for six rings, torque gradually fell to 2200 kN·m, thrust reduced to 18,000 kN, and discharge recovered to 95%. No spewing or over-excavation occurred. Cutterhead inspection revealed only soft clay residue and no hard mud cakes. Overall efficiency improved by approximately 40%.

Chemi Tech provides full-cycle support including product selection, injection parameter optimization and performance verification, all driven by real data. If you are dealing with clay-related mud cake or adhesion issues, contact our technical team via the official website or hotline for a tailored solution.