On December 30, the Qingdao Jiaozhou Bay Second Tunnel, the world’s largest undersea highway tunnel, officially started shield tunneling operations. The tunnel is expected to be completed and opened to traffic in December 2027.
According to reports, the shield excavation distance is 3,255 meters, and it is excavation from the Qingdao Port Terminal to the west coast. It will be connected with the drilling and blasting section tunnel, and the shield machine will be received and dismantled in the seabed cavern. The geological conditions on the seabed of Jiaozhou Bay are complex. The shield machine enters the sea immediately after setting off. It must traverse complex and changeable, unevenly soft and hard strata and fault zone strata over long distances. The “Haitian” shield machine used in the project has a total length of 142 meters and a total weight of. It has a capacity of 4,275 tons and an excavation diameter of 15.63 meters. It has intelligent systems such as a telescopic main drive and a telescopic excavation bin monitoring system. The integration of multiple innovative technologies and targeted layout have considerably improved the building and construction safety and security of the guard machine, ensuring that the protection tools can finish construction tasks safely, promptly, and efficiently. After the Jiaozhou Bay project is opened to traffic, Qingdao will break through the boundaries of urban space growth, which will have far-reaching significance in promoting the coordinated development of the east and west sides of Jiaozhou Bay and enhancing the overall competitiveness of the Jiaodong Peninsula urban agglomeration.
It is understood that the Jiaozhou Bay Secondly Tunnel Task begins with the West Coastline New District of Qingdao in the west, goes across Jiaozhou Bay in the east, and lands near Qingdao Port. It connects the urban area on the east coast of Qingdao in the form of an elevated bridge. The main line is 17.48 kilometers long, and the tunnel is 14.37 kilometers long. The sea section is 9.95 kilometers long, the main line tunnel shield machine excavation diameter is 15.63 meters, and the deepest point is 115 meters above sea level. The tunnel construction adopts the layout of two main tunnels and an intermediate service tunnel. It is constructed as a two-way, six-lane urban expressway with a design speed of 80km/h.
Application of concrete water-reducing agent in tunnel engineering construction
In tunnel construction, Polycarboxylate Superplasticizer can improve the fluidity of concrete, allowing the concrete to fill the tunnel formwork better, reduce the occurrence of pores and defects, and improve the overall quality and stability of the tunnel.
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