With the Haizhu Bay Tunnel, Guangzhou is constructing the first large-diameter tunnel using shield tunnelling. The used TBM therefor is nicknamed "Guangzhou First Shield". The double-tube, single-story tunnel passes under the back channel of the Pearl River, Luoxi Island, Sanzhi Xiangshui Road and finally Nanpu Avenue to connect to the bridge in the south of the project. The total length of the Haizhu Bay Tunnel is 4,348 meters, of which the mechanized tunnelling section is 2,077 meters. The main tunnel is a twin-tube tunnel with 6 lanes and an inner diameter of 14.5 meters. Geologically, the TBM can expect layers of mainly solid, medium-hard and slightly weathered, silty siltstone.

Challenges

• The excavation diameter is 15.07 meters, making it the largest tunnel under construction in Guangzhou.
• Ultra-shallow start and target shaft; maximum overburden 48 meters; maximum water pressure 5.2 bar.
• 2,077-meter-long bore under the Pearl River; soft at the top and hard at the bottom composite layer, long section through muddy siltstone layers.
• Complex environment, high building density above ground, extensive crossing of houses and rivers, high construction risk.
• In the start and finish area, the TBM crosses the foundations of buildings, which makes construction work more difficult.

Highlights

• Disc cutter change under normal pressure
• Retractable cutting wheel
• System for monitoring the rotation of the disc cutters
• Telescopic camera for monitoring the excavation chamber
• Separate flushing system for the cutting wheel center