The double-line subway tunnel successfully crossed Xiangjiang River.

　　In the early morning of November 19th, the shield machine of the Changsha-Zhuzhou-Xiangtan intercity railway "Chengtie No.2" safely passed through the Xiangjiang River water section and reached the eastern levee of Xiangjiang River. So far, the double-line Xiangjiang Tunnel of the intercity railway has successfully crossed the river, which marks a major breakthrough in the key lines of urban railway construction. According to the deployment, the city railway line west of Changsha Railway Station will strive to open to traffic by the end of 2017.

　　It takes about one year to excavate the 2.7 km section.

　　Xiangjiang Tunnel is one of the important control node projects in the construction of Changsha-Zhuzhou-Xiangtan intercity railway. Two shield tunneling machines are divided into two lines, from Binjiang Xincheng Station to Kaifu Temple Station from west to east, with a total length of 2.7 kilometers. In September and December last year, the shield machines "Chengtie No.1" and "Chengtie No.2" started from Binjiang New Town Station.

　　In the process of tunneling from west to east, the shield machine exits from Binjiang New Town Station, passes through Yinshan Road, then arrives at Changsha Shipyard, passes through the Xiangjiang River after passing through Yinpenling Bridge to the central line of Xiangjiang River, and then enters Kaifu Temple Station. The longitudinal section of the 2.7-kilometer interval excavation line is "V"-shaped, that is, it starts from Binjiang Xincheng Station and goes downhill all the way, then passes through Xiangjiang River and then goes uphill to enter Kaifu Temple Station. After a year of excavation, "Chengtie No.1" arrived at the east bank of Xiangjiang River in September this year. With the arrival of "Chengtie No.2" at the East Embankment in the early morning of November 19th, it means that the journey across the river of Xiangjiang Tunnel of Chengtie has been successfully completed.

　　At present, there are four river-bottom tunnels in Changsha, including Xiangjiang Tunnel of Metro, and the other three are Xiangjiang Tunnel of Yingpan Road, Xiangjiang Tunnel of Nanhu Road and River-crossing Tunnel of Metro Line 2. Metro Line 3, which is scheduled to start within this year, is also planned to cross the river, and it will become the fifth tunnel under the Xiangjiang River bed after completion.

　　Crossing the Xiangjiang section is 1.1 kilometers long.

　　"The Xiangjiang Tunnel crosses the Xiangjiang section for 1,100 meters, and the minimum buried depth of the bottom section of the shield tunnel is only 10 meters." According to the person in charge of the Changsha-Zhuzhou-Xiangtan Intercity Railway Project Department of China Railway Tunnel Group, the geological conditions around the tunnel construction scope are complex, and it is the main difficulty to effectively control the pressure of the shield silo and avoid the collapse, roof caving and gushing at the bottom of the river. At the same time, in long-distance underwater excavation, tool protection and tool replacement are also the key to ensure safe excavation. Combined with the geological conditions of Changsha section of Xiangjiang River, large excavation section of tunnel, precise axis control and other requirements, the function configuration of two shield machines crossing Xiangjiang River has been carefully improved.

　　The length of the shield of the city railway is 112 meters, the diameter of the cutter head is 9.34 meters, and the tunnel dug is equivalent to three stories high. During the excavation of this "behemoth" in the underground, a circle of segments is installed to support the tunnel every 1.8 meters, forming the main structure of the tunnel one by one. The driver controls the shield machine to move forward in the underground, and the monitoring personnel in the ground dispatching room monitor the tunneling status 24 hours through the shield parameters, and the tunneling monitoring is accurate to the millimeter, so as to ensure that the shield machine moves accurately according to the construction design route. During the 1-year-long excavation process, the two shield machines advanced steadily in tandem, and the maximum daily excavation distance was 18 meters.

　　Metro plans to go under Sanxiang Nanhu Market.

　　After the shield machine arrived at the levee on the east bank of Xiangjiang River, it continued to advance to Kaifu Temple Station.

　　In the area north of Changsha Railway Station, Changsha-Zhuzhou-Xiangtan Metro originally planned to cross Sanxiang Nanhu Market in the form of viaduct, that is, after the metro line was led out of Changsha Railway Station, it crossed Yuanda Road and Sanxiang Nanhu Market northward through viaduct. In the process of scheme optimization, it is found that if a viaduct is erected, the amount of demolition along the viaduct is large, which is not conducive to the overall planning and development of the area. A large number of demolition can be avoided by using a tunnel to cross the area. To this end, Changsha-Zhuzhou-Xiangtan Urban Railway Construction has applied for the design change of "bridge to tunnel" on the section of Sanxiang Nanhu Market, and the application for this change is waiting for approval.　

　　If the "Bridge to Tunnel" scheme is implemented as scheduled, the two shield machines of Xiangjiang Tunnel will be hoisted out from Kaifu Temple Station and transported to the starting shaft located in the north of Changsha Railway Station, and the excavation of the shield tunnel under Sanxiang Nanhu Market will continue.