On the morning of June 19, with the welding of the last steel box girder completed, the Huangmaohai Bridge of the Huangmaohai Cross-Sea Channel project successfully achieved closure, linking Jiangmen and Zhuhai across the Huangmaohai sea area west of the Pearl River. Reporters learned on site that, as the first cross-sea channel project to commence construction after the release of the Outline Development Plan for the Guangdong-Hong Kong-Macao Greater Bay Area, the project is the western extension of the Hong Kong-Zhuhai-Macao Bridge, and this closure lays a solid foundation for completion and opening to traffic by the end of 2024.

The Huangmaohai Cross-Sea Channel project has a total route length of about 31 kilometers, with a sea section of about 15 kilometers. It features two main bridges, the Gaolan Port Bridge and the Huangmaohai Bridge, of which the Gaolan Port Bridge achieved closure on March 20 this year. The Huangmaohai Bridge, closed this time, spans two navigation channels in the Huangmaohai sea area and adopts a unique design of three towers and two spans. It is a cable-stayed bridge using a single-column pylon, double-cable-plane, fully floating system, jointly constructed by China Railway Major Bridge Engineering Group, Poly Changda, and China Railway Baoqiao.

The Huangmaohai Bridge has a single span of 720 meters and a total length of 2,200 meters. The entire bridge comprises 16 types of girder segments, totaling 149 segments, with the heaviest steel box girder weighing 420 tons. The deck adopts a split-type steel box girder design, consisting of two steel box girders and transverse connecting boxes, with a total deck width of 50.4 meters, the widest among bridges of its type in the province. This is also the first large-scale application of split-type steel box girders in Guangdong Province.

"The hoisting of the main bridge steel box girders was scheduled during the typhoon-prone season, posing great challenges to the main girder construction," emphasized Zhu Chao, director of the Huangmaohai Cross-Sea Channel Management Center. Since the successful erection of the first steel box girder of the Huangmaohai Bridge in October 2023, they have been "threading the needle" in the variable climate of the Huangmaohai sea area. In response to safety risks and technical difficulties in navigation safety assurance and typhoon defense measures, they conducted in-depth research on plans and measures. After nine months, the closure was finally achieved with a deviation of less than 2 millimeters.

"We changed the vortex-shedding frequency of the pylon by varying its cross-section, avoiding single-frequency resonance problems. Through comprehensive optimization and innovation in multiple mechanical designs, we were the first to propose an integrated aerodynamic control measure of 'wind fairing + horizontal vortex-suppression plates + lower central stabilizer plate,' and calculated that the bridge's vortex-induced vibration performance within the actual operating wind speed range is superior to the strictest international comfort standards," Zhu Chao emphasized. "The 'central split-type steel box girder + single-column pylon' scheme enables the Huangmaohai Bridge to withstand Category 17 typhoons."

"Through precise simulation and intelligent data collection, we monitored the entire steel box girder hoisting process, and established special control procedure acceptance systems such as 'one girder, eight meters' and 'one cable, two meters,'" said Sun Wenjin, manager of the Engineering Department of the Huangmaohai Cross-Sea Channel Management Center. According to third-party testing, the one-time pass rate for circumferential welds exceeded 99%, and the one-time pass rate for final tightening torque of high-strength bolts at the bridge site reached 100%. The hoisting of steel box girders was shortened from 10 days per pair to 5 days per pair, with all indicators meeting specification requirements.

"We adopted portable and movable welding robots, achieving fully automated and intelligent welding of structures such as diaphragms, with a one-time weld inspection pass rate of over 99%," introduced Sha Junqiang, deputy general manager and chief economist of China Railway Baoqiao (Zhoushan) Company.

After the closure of the Huangmaohai Bridge, the project will officially commence pavement construction and steel box girder deck paving, with completion and opening to traffic expected by the end of 2024. Once completed and open to traffic, Jiangmen will be only 30 minutes from Zhuhai Jinwan Airport and 60 minutes from Hong Kong International Airport. Upon completion, the Huangmaohai Bridge will join the Hong Kong-Zhuhai-Macao Bridge, the Shenzhen-Zhongshan Link, the Nansha Bridge, and the Humen Bridge to form a cluster of cross-sea and cross-river channels in the Guangdong-Hong Kong-Macao Greater Bay Area.