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　　On May 29, “Yangtze Vanguard,” a domestically-produced full-diameter tunnel boring machine, began cross-river tunneling for the metro line 12 of Wuhan’s rail transit. It marked the beginning of the cross-Yangtze-River construction of Asia’s longest rail transit loop.

　　The metro line 12 project of Wuhan’s rail transit is jointly funded by China Railway and private businesses, carried out by China Railway Development Investment Group Co., Ltd., and constructed by China Railway Tunnel Group. With a total length of 59.9 kilometers, the metro line has 37 stations. The cross-river tunnel project from the South International Expo Center Station to the Lingwu Village Station is a control project for the entire metro line. Measuring 3.37 kilometers in length, the tunnel project goes under the Yangtze River twice, the Hanjiang River one time and lakes twice. The maximum depth is 55.17 meters, the average water depth is 34.85 meters, and the maximum hydraulic pressure is 7.4 Pa. The tunneling follows a V-shape pattern and the maximum gradient is 25.29‰.   

　　The “Yangtze Vanguard” TBM, jointly developed by China Railway Tunnel Group and China Railway Engineering Equipment Group Co., Ltd., is the first domestically-produced full-diameter TBM to be used by Wuhan in its rail transit construction. Its diameter reaches 12.56 meters, as high as a four-story building and about four times that of an ordinary TBM. With a total weight of 2,900 tons and a length of around 105 meters, the machine is a real essential for infrastructure construction.