Recently, the right-line tunnel boring machine (TBM) tunnel of the Nanjiao-Xichang section (hereinafter referred to as the "Nanxi Section") of Guangzhou Metro Line 22's post-opening segment has been completed, marking the second dual-line tunnel to achieve full connection within this segment.
The construction of the upcoming Guangzhou Metro Line 22's post-opening segment (from Chentougang to Fangcun) has achieved a significant milestone, with 76% of its civil engineering works completed to date. Out of the four stations planned, three have successfully reached the roof closure stage, while the remaining one is actively undergoing civil construction.
Among the four tunnel sections, two have already been fully excavated and connected, while the other two are progressing steadily with civil works. A total of four TBMs are currently in operation, driving forward the project's progress.
One of the most formidable challenges encountered during the civil construction phase has been the intricate geological conditions at Nanjiao Station. As an ultra-deep excavation site with a maximum depth approaching 29 meters, the station's foundation pit lies within a moderately weathered rock layer, overlaying extensive areas of weak soil (sand and silt layers) that can reach up to 14 meters thick in some sections. The poor self-stability and high water content of these layers pose a high risk of water leakage, sand boils, and ground subsidence, significantly complicating construction efforts.
The right-line tunnel of the Nanxi Section, spanning approximately 2.3 kilometers, traverses a diverse range of structures, including industrial factories, highways, major bridges, and aging buildings. The long tunnel length, coupled with significant variations in burial depth, presents formidable challenges, particularly at the initial TBM launching site, where the geology transitions from soft sand layers above to hard rock below. This challenging geological interface can lead to ground settlement and difficulties in TBM tunneling.
To overcome the obstacles posed by the thick, weak sand layers at the tunnel crown and the challenge of crossing rivers, project teams organized numerous consultations with internal and external experts. Through optimizing TBM configurations and construction methodologies, they introduced an additional mud-water circulation system at the launching section and equipped it with advanced grouting systems to reinforce the weak strata ahead of the excavation face. These measures ensured safe tunneling and chamber opening operations within the problematic soil layers.
Furthermore, the integration of intelligent real-time monitoring systems for the TBMs, including soil chamber visualization, automated spoil weighing, and automatic shield tail gap measurement, has significantly enhanced operational safety by providing real-time insights into tunneling progress.
To guarantee the quality of the completed tunnels, grouting systems have been installed at the rear of the tunnel boring machines, enabling timely grouting and filling of the tunnel lining. This effective measure has prevented water leakage and ground subsidence, ensuring the structural integrity of the tunnels.
The ongoing progress of Line 22 underscores the commitment to delivering a seamless transportation network that will connect Fangcun directly to Guangzhou South Railway Station, revolutionizing future commuting patterns and fostering greater connectivity within the metropolis.
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