At 7:00 on May 14, 2016, builders of the Hong Kong-Zhuhai-Macao Bridge overcame major difficulties such as large runoff, strong siltation, and GPS signal loss, and after 24 hours of continuous construction, successfully completed the precise docking of the E26 immersed tube for the bridge's undersea tunnel. At this point, the total length of the tunnel built in the island and tunnel project has reached 4,545 meters. 　　On March 31 this year, the installation of the E25 immersed tube faced the challenge of strong siltation. The island and tunnel project department comprehensively analyzed risks, made scientific decisions, and started the floating and installation construction 25 hours in advance, winning a tough battle against sediment. The builders did not stop and subsequently began preparations for the installation of the E26 immersed tube. However, due to the expanding sand mining operations in the surrounding waters, the impact on the siltation of the immersed tube tunnel trench continued to increase. On-site monitoring data showed that the siltation in the trench increased day by day, exceeding the allowable conditions for immersed tube installation. To ensure the 120-year design service life of the undersea tunnel, the project department decided to abandon the installation window in late April.
　　On April 30, Xu Shaohua, member of the Standing Committee of the Guangdong Provincial Party Committee and Executive Vice Governor, held an on-site meeting at the bridge construction front line, emphasizing that when there is a conflict between sand mining and engineering construction, priority should be given to ensuring the placement of immersed tubes. On May 3, the provincial government decided to stop sand mining operations in the Wailingding sea area. Under the overall coordination of the Hong Kong-Zhuhai-Macao Bridge Authority, the Guangdong Provincial Ocean and Fisheries Bureau, the Guangdong Maritime Safety Administration, and other parties coordinated and cooperated, and all relevant parties fully supported the bridge construction. All sand mining vessels evacuated the site as required, creating a good environment for the immersed tube tunnel construction. The island and tunnel project department immediately restarted preparations for the installation of the E26 immersed tube, seized the operation window, and fully advanced the undersea tunnel construction. 　　Affected by recent continuous heavy rainfall, the runoff of the Pearl River Basin increased significantly, reaching more than 30,000 m3/s, far exceeding the marginal conditions that the immersed tube installation could withstand. Although they had experience in completing floating and installation under large runoff conditions below 20,000 m3/s, the island and tunnel project builders, with rich offshore construction experience, were even more aware of the power of "large runoff"—unpredictable changes in surface flow velocity, stratified flow phenomena in seawater, and increased seawater turbidity would all bring uncontrollable risks to floating and docking. To this end, the project department closely monitored weather changes, strengthened on-site near monitoring, formulated and implemented response plans, and conducted multiple drills for floating and immersion under large runoff conditions, making every effort to prepare for the immersed tube installation. 　　At 21:30 on May 12, less than 10 hours before the scheduled undocking time, the on-site decision-making meeting for the installation of the E26 immersed tube was held at the immersed tube prefabrication plant. The on-site decision-making group conducted a comprehensive analysis of the latest ocean current monitoring, siltation conditions, and the construction environment of each stage of the immersed tube floating and installation. In view of the lingering impact of sand mining operations in the surrounding waters and the unfavorable condition that the average daily siltation in the trench exceeded twice the normal level, it was decided to start the floating operation half an hour earlier than originally planned to accelerate the floating and installation construction and make the greatest effort to reduce the impact of strong siltation.
　　At 6:30 on May 13, Lin Ming, general manager of the island and tunnel project, issued the "start work" order, and the E26 immersed tube slowly moved out of the dock entrance by winching for formation operations.
　　At 6:40, the project department held another floating safety briefing on site, requiring the floating captain to pay close attention to the impact of large runoff, strengthen the cooperation of the towing fleet, control the towing speed, and promptly respond to emergencies to ensure the safety of the immersed tube floating. 　　At 9:00, the formation was completed. Escorted by more than 10 maritime warning vessels, current measurement vessels, and on-site monitoring vessels for the floating channel, the E26 immersed tube headed to the installation sea area. Facing the harsh sea conditions with strong winds and rough waves at departure, the experienced floating captain commanded 12 tugboats to work closely together, skillfully using the floating control system to safely escort the immersed tube through the waves. At 13:40, the E26 immersed tube safely arrived at the construction sea area and began mooring operations. At 22:30, immersion construction began. 　　After several rounds of immersion, monitoring, and adjustment, when the E26 immersed tube was about to be docked, the GPS signal was lost. Facing this sudden challenge, the builders made full use of their mature installation experience, repeatedly measured, compared, and corrected, accurately controlled the posture and position of the immersed tube, and continuously improved the docking accuracy. At 7:00 on May 14, the immersed tube pulling and hydraulic connection operations were completed successively. The breakthrough measurement showed that all indicators met the design standards, and the installation of the E26 immersed tube was a complete success.