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The submarine tunnel of the Hong Kong-Zhuhai-Macao Bridge consists of 33 immersed pipe joints and a final joint. The final joint is connected with the immersed pipe joints underwater. The floating crane is used to hoist the final joint in place, and the embedded hydraulic jack system is started. The pushing trabecular structure moves away from the main body of the final joint, driving the tension of the M water stop belt. After moving to a certain distance, the Gina water stop belt at the end of the pushing trabecular reaches the steel cap of the adjacent pipe section, and the Gina water stop belt is pressed tightly, which is realized. The internal and external isolation of the pipe joints, and finally the drainage of the pipe joints, forming a weldable space, the welding of steel joints in this space, the relevant structure relationship refers to Fig. 1. The steel joint consists of inner ring connecting steel plate, outer ring connecting steel plate, small stiffening and partition system. On the cross section of the tunnel, the partition is arranged in one gear at intervals. Connecting steel plates are manufactured in factories and shipped to the tunnel installation site. After the welding of steel joints is completed, a permanent enclosed interior is formed, high fluidity concrete is poured into it, the connection of the tunnel is completed and the final connection is achieved. There are a lot of upside-up welding operations in the welding of connecting steel plates, and the working space is limited. There is no experience for reference at home and abroad. There are the following difficulties:

(1) The construction environment is bad and the welding space is limited. The welding of the steel joint is carried out under the temporary water stop condition of Gina, and combined with the humid environment inside the chamber, without natural ventilation conditions, the net working space between the joint and the steel cap is only 1 m.

(2) The workload of the weld of the steel joint is large and the quality of the weld is high. The butt weld must be fully penetrated and 100% of the weld must pass UT/MT flaw detection.

(3) The construction period of steel joint welding must be as short as possible. The risk is too high because only GINA water stop is pushed by cylinder to isolate seawater before welding of steel joint is completed. Therefore, it is an effective guarantee for the safe penetration of immersed pipe engineering to complete the welding of steel joint and steel plate in the joint cavity as soon as possible.

(4) The workload of transporting components to the combined chamber is large, the labor intensity is high and the safety risk is high. We adjust the steel joint connection plate from the following aspects to effectively reduce the difficulty of on-site welding of the steel joint connection plate.

(1) Optimize the division of steel joint connection plates, reduce the length of field welding, and effectively reduce the difficulty of field welding.

(2) Hanging part of the connecting steel plate of the steel joint to the structure of the final joint (in the factory) can reduce the carrying capacity of the connecting steel plate on the construction site, greatly reduce the labor intensity and reduce the safety risk.

(3) Improve the structure of steel joint to enhance the stability and safety of the whole structure during the welding process.

Overview of structural optimization of metal joints