The final piece of the undersea tunnel of the Shenzhen-Zhongshan Link of the Guangdong-Hong Kong-Macao Greater Bay Area was attached on Sunday, marking the closure of the world's longest and widest undersea tunnel after five years of construction.

Located in the lower reaches of the Pearl River estuary, the Shenzhen-Zhongshan cross-sea link project is 24 kilometers long, composed of 32 tubes and one final joint. The tunnel includes five kilometers of undersea tube.

Previously, a total of 31 tubes were dropped into place from the east and the west to the middle, then aligned with the others. The last tube module E23 was connected to the E24 tube on the east side on Sunday.

According to Liu Jian, director of the chief engineer’s office at the Shenzhen-Zhongshan Link Management Center, the steel consumption of each tube is about 10,000 metric tons, with the weld length exceeding 270 kilometers and the thickness of the steel plate reaching 40 millimeters. A standard tube is 165 meters long, 46 meters wide and 10.6 meters high, and its volume is equivalent to a 55-story building.

The Shenzhen-Zhongshan Link is scheduled to drill through in November 2023 and go into operation in 2024.

The link connecting the cities of Shenzhen and Zhongshan will play an important role in developing the Guangdong-Hong Kong-Macao Greater Bay Area.