The earth pressure balance shield machine is an advanced mechanical equipment widely used in underground tunnel construction. It realizes continuous tunnel excavation by establishing a stable earth pressure environment on the excavation surface. This technology is particularly suitable for tunnel construction in soft soil and clay strata.

   The basic principle of the earth pressure balance shield machine is to use a tangible steel component to excavate the soil along the tunnel design axis and advance forward. A closed soil cavity is formed in front of the cutterhead of the shield machine. While the cutterhead rotates to cut the stratum, the cut soil is transported into the soil cavity. By controlling the balance between the soil pressure in the soil cavity and the groundwater pressure and the stress of the surrounding soil, the ground settlement or uplift is prevented, ensuring the safety and stability of the tunnel construction. At the same time, the shield machine is equipped with a propulsion system, a soil discharge system and a guide system to achieve efficient and automated tunnel excavation.

   When the shield machine is advancing, its front cutterhead rotates to excavate the stratum soil, and the cut soil enters the soil cabin. When the soil in the soil cabin is full, its passive soil pressure is basically balanced with the soil pressure and water pressure on the excavation surface, so that the excavation surface and the shield surface are in a stable state. Then, the ballast soil (i.e. excavated waste soil) is discharged to the soil box and transported to the surface through a screw conveyor. The amount of soil discharged is controlled by a sliding gate or a rotating funnel installed at the soil discharge port of the screw conveyor to ensure the stability of the excavation surface.

   Compared with traditional dark excavation construction, the earth pressure balance shield construction mode can greatly reduce the stress loss of the stratum and reduce the impact on the surrounding environment and groundwater resources.

   Earth pressure balance shield machines are widely used in tunnel construction in urban subways, railways, highways, water conservancy projects, municipal pipelines and other fields due to their advantages such as small impact on the surface, high construction efficiency and high degree of automation. Especially in urban areas with dense populations and numerous buildings, earth pressure balance shield machines can carry out construction without affecting ground traffic and residents' lives, and have important social and economic value.