Nanjing Yangtze River Five Bridge Jiajiang Tunnel Excavated the Largest Highway Shield Tunnel in China

On the morning of December 26, with the “New Era” shield machine cutter slowly starting, the A3 Bridge Jiajiang Tunnel Project of the Nanjing Yangtze River Fifth Bridge, which was built by the China Railway 14th Bureau Group, was successfully burrowed, marking the diameter of the excavation. The largest diameter highway shield tunnel of 15.46 meters in China entered the main construction stage.

According to Shi Qingtao, the person in charge of the 14th Bureau of China Railway, the tunnel is designed as a two-hole two-way six-lane with a speed of 80 km/h. The total length of the tunnel is 1159 meters, the outer diameter of the tube is 15 meters, and the diameter of the excavation is 15.46 meters. It is a rare super large diameter shield tunnel in China. The shield machine is 140 meters long and weighs more than 3,500 tons. It has a constant pressure tool change function. A total of 237 different types of tools are installed, and one third of them can be used for normal pressure tool change.

The shield crosses the Jiajiang River and the construction risk is high. The shallowest covering soil at the beginning of the project is 7.1 meters, less than 0.5 times the tunnel diameter, which is the origin of shallow covering soil. The deepest part is 41.6 meters and the water and soil pressure is 4 bars. The depth of the foundation pit is 38.9 meters, which is equivalent to the height of the 13-storey underground. It belongs to the first ultra-deep foundation pit in Nanjing. The project is located in Jiangxinzhou Ecological Science and Technology Island, close to Jiajiang drinking water source protection site, and has high requirements for environmental protection and green construction.

The Fifth Yangtze River Bridge in Nanjing is a collinear passage between the 205 National Highway and the 312 National Highway across the Yangtze River. It is located about 5 kilometers downstream of the Yangtze River Third Bridge and about 13 kilometers upstream of the Yangtze River Bridge. As the seventh road crossing channel in Nanjing, it is an important link connecting the main urban area with the Jiangbei New District. It is also an important part of the Nanjing “High Speed ​​Road System”. After the completion of the project, it will form a fast road network of “Tianzi Expressway” + “Fast One Ring”. It is an important hub connecting the main city and Jiangbei New District. It plays an important role in alleviating traffic pressure and developing Jiangbei New Area.

The construction unit China Railway 14th Bureau Group is a backbone enterprise and leading enterprise in the field of large-diameter shields and underwater shields and urban rail transit. It has successively built the Nanjing Yangtze River Tunnel and the Nanjing Metro Line 10 Cross-river Tunnel, etc., and has core construction technology in the field of large-diameter shield construction in China. At present, four Yangtze River shield tunnels have been built and four Yangtze River shield tunnels are under construction.