The picture shows the starting site of the "Guoxin" shield machine for the second Jiaozhou Bay undersea tunnel. [Photo/sasac.gov.cn]
On June 30, the "Guoxin" shield machine for the second Jiaozhou Bay undersea tunnel made its debut at wharf No. 8 of the Port of Qingdao, Shandong Province. This marks the official excavation of the shield section of the second Jiaozhou Bay undersea tunnel project - the world's longest subsea road tunnel. The project was invested by Qingdao Guoxin Development Group, designed and constructed by subsidiaries of China Railway Construction Corporation Limited.
The picture shows the aerial photo of the starting tunnel shaft. [Photo/sasac.gov.cn]
The second Jiaozhou Bay undersea tunnel project is the world's largest and longest subsea road tunnel. The main line of the project is 17.5 kilometers long. Spanning Jiaozhou Bay, the tunnel will connect the eastern and western parts of Qingdao. It stretches from Huaihe East Road in Qingdao West Coast New Area in the west, to Liugongdao Road and then to the Port of Qingdao in the east to join the East Coast. The tunnel is 14.37 km long, 9.95 km of which is under the sea. It is designed with six two-way lanes, plus a service channel in the center. The shield section of the tunnel is 3,253 meters long, and three shield machines are used in construction, including two main shield tunneling machines with a diameter of 15.63 meters and a service shield tunneling machine with a diameter of 8.18 meters.
The picture shows the scene of the tunneling launching ceremony. [Photo/sasac.gov.cn]
The second undersea tunnel of Jiaozhou Bay has complex geological conditions, passing through multiple fractured zones and soft and hard strata. The tunnel will be excavated over a long distance in hard rock, with a maximum water pressure of 0.96 megapascals. Based on different geological conditions and the construction environment, the project adopts a combined drilling, blasting and shield tunneling method to cross Jiaozhou Bay.
The picture shows the scene of the tunnel launching ceremony. [Photo/sasac.gov.cn]
The "Guoxin" service shield tunneling machine has an excavation diameter of 8.18 meters, a total length of 180 meters, and a total weight of 1,686 tons. It is equipped with a telescopic main drive, a telescopic excavation monitoring system, a mud circulation system, and a SAMSON pressure holding system. It has applied a number of cutting-edge technologies such as synchronous double-liquid grouting and synchronous assembly. The main bearing has four outer seals and three inner seals, and can withstand a maximum excavation face pressure of up to 1.2 MPa to ensure safe and stable excavation. In addition, according to the construction conditions and project characteristics, the construction team designed and adopted high-strength and high-impermeability reinforced steel fiber concrete segments, and realized the simultaneous construction of the substructure in the 8-meter-level shield tunnel for the first time through the special design of prefabricated box culverts, which provides technical support and ensures safe and efficient construction.
The picture shows technicians starting up the shield machine in the operating room. [Photo/sasac.gov.cn]
The second undersea tunnel of Jiaozhou Bay is expected to be completed and put into operation in December 2027. Once completed, it will have far-reaching significance in optimizing the urban spatial layout and enhancing the overall competitiveness of the Jiaodong Peninsula's urban agglomeration.
(Executive editor: Xie Yunxiao)
