On September 5, 2008 (August 6, 2008 in the lunar calendar), the "First Tunnel of the Thousand Miles Yangtze River" was connected to two tracks. On September 5, 2008, tunnel builders celebrated the opening of the tunnel on the shield at the acceptance well on Changxing Island, Shanghai. On that day, as the ultra-large diameter shield successfully entered the Shanghai Changxing Island receiving shaft, the world's largest diameter shield tunnel-the Shanghai Yangtze River Tunnel Project achieved two-track connection. The Yangtze River Tunnel, known as the "First Tunnel of Thousands of Miles of Yangtze River", is about 8. 9 kilometers, the tunnel has an inner diameter of 13. 7 meters, the outer diameter of the tunnel is 15. 43 meters, which is the world's largest diameter shield tunnel. The deepest burial depth will reach 55 meters. On December 28, 2004, the Shanghai Yangtze River Tunnel Project, a national large-scale transportation project, was launched, and Shanghai Tunnel Co., Ltd. was responsible for the construction of the tunnel project. This ultra-large tunnel is located in the northeast of Shanghai City, connecting the land area of Shanghai City and Changxing Island. The tunnel is about 8. 9 kilometers, divided into upper and lower floors, the upper layer is a dual-tube two-way six-lane expressway, and the lower layer is reserved for Shanghai Rail Transit Line 9 to cooperate with the Shanghai Chongming, Changxing and Hengsha "three-island linkage" development plan.