Shield machine has a history of nearly 200 years, which started in Britain and developed in Japan and Germany.
In the past 40 years, through the exploration and research of EPB and slurry shield machine's key technologies, such as effective sealing of shield machine, ensuring the stability of excavation surface, controlling the surface uplift and collapse within the specified range, the service life of tools and the replacement of tools under sealed conditions, and the treatment technology of some harsh geological conditions such as high water pressure, the shield machine has been developed rapidly. Due to the rapid development of economy and the needs of practical engineering, shield machines, especially earth pressure balance shield machines and slurry shield machines, have developed rapidly in Japan.
Germany's shield machine technology is also unique, especially in the process of underground construction, the premise of sealing and replacing the cutter head under the condition of air pressure as high as 0.3MPa is guaranteed, thus improving the first tunneling length of the shield machine. Germany has also developed tools to replace worn tools from the atmospheric space inside the large-diameter cutter head under sealed conditions.
Extended data
The shield machine stabilizes the excavation face by pressurizing mud or mud (usually bentonite suspension), and there is a sealing partition behind its cutter head to form a mud chamber with the excavation face, which is full of mud. The mixture of excavated soil and mud is transported by mud pump to the separation plant outside the hole, and the separated mud is reused.
Earth pressure balance shield machine takes soil material (adding foam to improve soil if necessary) as the medium to stabilize the excavation face, and forms a soil chamber between the rear partition of the cutter head and the excavation face. The cutter head rotates to dig to increase the soil material, and then the screw feeder rotates to transport the soil material out. The earth pressure in the soil chamber can be adjusted by the rotating excavation speed of the cutter head and the excavation amount (rotation speed) of the screw feeder.
According to the classification of shield machines, shield tunneling methods can be divided into: open excavation, mechanical cutting, grid format and extrusion. In order to reduce the disturbance of shield construction to the stratum, the shield can be driven by jack to make its incision penetrate into the soil layer, and then the soil can be excavated and transported in the incision.
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