The urban underground space is limited and the geological conditions are complex, making the parallel construction of large-diameter shield tunneling at close range a difficult problem in the industry. The CR21G construction team overcame difficulties, broke through multiple technical barriers, and successfully completed the double line connection of China's first parallel large-diameter shield tunnel with the smallest clear distance, setting a new record for similar construction in China.

The construction challenge is extremely rigorous

The tunnel of the Huachengjie Station distribution section that was connected this time belongs to the Guangzhou Hualien Intercity Railway. Huachengjie Station, as the terminal station of the line, has a total length of 735 meters, a single track length of 265.52 meters, and a tunnel excavation diameter of 12.06 meters. Due to the limitations of urban underground space, the clear distance between the left and right tunnel segments is only 1.14 meters, making it the first large-diameter shield double line tunnel in China to achieve extremely small clear distance parallel construction. Large diameter shield tunneling will significantly disturb the geological strata, coupled with the influence of double tunnel soil stress, which can easily cause pipe misalignment, tunnel leakage, and structural deformation. The construction risks and technical difficulties rank among the top in the industry.

Innovative technology solves difficult problems

In response to complex geological and extreme construction conditions, the project team has implemented multiple innovative construction techniques. Build a 0.6-meter-thick fiberglass reinforced underwater concrete continuous wall in high-risk areas with weathered and fractured double track tunnels and developed limestone caves, effectively preventing stress accumulation during double track construction. At the same time, traditional connection structures are replaced with new types of longitudinal seam sliding in and circumferential seam insertion quick connectors, greatly improving the accuracy of pipe segment assembly. During the construction period, a 10 meter long intelligent internal support trolley will be used to provide real-time protection and intelligent monitoring of the formed tunnel, comprehensively avoiding the risk of construction deformation.

Empowering the development of transportation in the Bay Area

The successful completion of the double track tunnel fully validates the feasibility and stability of the large-diameter shield construction technology under extremely small clearance conditions, filling the gap in similar construction technology in China and accumulating mature practical experience for the construction of complex urban underground tunnels nationwide. After the completion of the Guangzhou Hualien Intercity Project, it will seamlessly connect with Metro Line 18 for operation, linking the north-south transportation network of the Guangzhou metropolitan area, improving the rail transit network of the Guangdong Hong Kong Macao Greater Bay Area, effectively enhancing regional commuting efficiency and interconnectivity, and supporting the high-quality development of integrated development in the Bay Area.Editor/Min Jing