Recently, the left-line shield tunnel of the Nanjiao to Xilang section (referred to as the "Nanxi section") of the Guangzhou Metro Line 22 extension was successfully completed, making it the first finished tunnel in Liwan District for this segment.
The left line of the Nanxi section stretches approximately 2.3 kilometers. The section posed significant challenges due to its long shield tunnel, varying depths, and difficult geological conditions, such as soft upper layers and hard lower layers from the start. The route also involved risks like tunneling beneath factories, highways, old buildings, and large bridges, making the construction particularly challenging.
To ensure the safety of the project, Guangzhou Metro collaborated with China Tunnel Construction Group Co, Ltd. Guangdong and Guangzhou Metro Engineering Consulting, and organized multiple expert consultation meetings.
They scientifically developed construction plans, optimized the selection of the shield machine, and equipped it with an advanced grouting system to reinforce the soft soil ahead of the tunnel face, allowing safe and smooth excavation through weak soil layers.
In addition, the shield machine was outfitted with intelligent systems such as visual monitoring of the excavation chamber, automatic weighing of transported soil, and automatic measurement of the shield tail gap. These systems enabled real-time monitoring of the tunneling process.
To address challenges of tunnel water seepage and ground settlement control, an additional grouting system was installed at the rear of the shield trolley to promptly fill and reinforce the completed tunnel, ensuring its quality.
Furthermore, the construction team has established a regular communication mechanism with relevant authorities and government departments to manage various sources of risk. They have arranged 24-hour on-site supervision during the tunneling process, continuously optimizing construction parameters based on monitoring data to ensure the safety and control of the tunneling operations.
As of now, 68% of the civil engineering work for the Line 22 extension has been completed. Of the four stations, two have been topped out and two are undergoing civil construction. Out of the four sections, one has been completed and three are under construction, with a total of five shield machines currently in operation.
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