With the continuous and vigorous investment of various countries in the construction of urban transportation infrastructure, many large-scale cross-sea and river-crossing shield tunnel projects have been built at home and abroad (such as the Tokyo Bay Subsea Tunnel in Japan, the "Green Heart Tunnel" in the Netherlands, the Wuhan Yangtze River Tunnel, and the Nanjing Yangtze River Tunnel Etc.), large-diameter tunnels have become one of the trends in the development of tunnel engineering. Slurry shield construction technology has the advantages of not requiring special soil improvement, strong geological adaptability, relying on slurry to form a mud film on the excavation surface to resist soil water pressure, and high stability of the excavation surface. It is used in large urban tunnels and large river crossings. Tunnel construction has been widely used, such as the Shanghai Yangtze River Tunnel, Dalian Road Tunnel, Fuxing East Road Tunnel, etc., which have been built in Shanghai, are all slurry shield tunnels.

The working principle of the slurry balance shield is mainly to install a partition behind the cutter head of the shield machine, and a sealed slurry pressure chamber is formed between the cutter head and the partition. The pressurized slurry is transported to the slurry during the construction of the shield tunnel. Pressure chamber; muddy water forms a layer of mud film on the excavation surface under a certain pressure to balance the water and soil pressure on the excavation surface. At the same time, the cutter head rotates and cuts and advances in the muddy water environment. The soil under the cutting mixes with the slurry in the muddy water pressure chamber to form high-concentration slurry, which is then pumped out by the muddy water pump and transported to the ground through the mud pipe. At the same time, fresh muddy water is processed and added through the circulating muddy water system to maintain the balance and stability of the excavation surface and control ground subsidence.