What is the shield mud-water balance

The mud water shield machine uses pressurized mud water or mud (usually bentonite suspension) to stabilize the excavation surface. On the back side of the cutter head of the mechanical shield, there is a sealed partition behind the cutter head to remove water, the muddy water made by mixing clay and its additives is pressed into the muddy water tank through the conveying pipeline. When the muddy water fills the whole muddy water tank and has a certain pressure, a muddy water pressure chamber is formed. The excavated soil material and mud are mixed and transported by the mud pump to the outside of the cave for separation. Plant, the mud is reused after separation.

The earth pressure balance shield machine uses soil material (add foam if necessary to improve the soil) as a medium for stabilizing the excavation surface. A soil chamber is formed between the partition behind the cutter head and the excavation surface, and the cutter head rotates for excavation. The soil material is increased, and then the soil material is transported out by the rotation of the screw conveyor. The soil pressure in the soil chamber can be adjusted by the rotating excavation speed of the cutter head and the excavation volume (rotation speed) of the screw feeder.

Through the pressurization of mud water and the pressure maintaining mechanism, the stability of the excavation face can be maintained.

When the shield is advancing, the soil and sand cut by the rotating cutter are stirred by the stirring device to form high-concentration muddy water, which is sent to the ground mud-water separation system by means of fluid transportation, and the ballast soil and water are separated and then sent back to the mud-water silo. The main characteristics of the pressure-balanced shield method.

Because it is the muddy water pressure that makes the cutting surface stable and balanced, it is named muddy water pressurized balance shield, or muddy water shield for short.