At the confluence of two rivers and a city of a hundred lakes, the great rivers and lakes are a reflection of Wuhan's unique geographical advantages, but also a natural barrier to urban transportation development. The Wuchang area is home to over 20 lakes, including Tangxun Lake, China's largest urban lake, and East Lake, the second largest. To address the poor north-south traffic caused by lakes, Wuhan proposed the grand concept of building a new underground passage to connect East Lake and South Lake. Against this backdrop, at the end of June 2020, the long-awaited Two Lakes Tunnel Project officially broke ground.

Rendering of the Zhuodaoquan North Road ground section

The Two Lakes Tunnel starts from Qinyuan Road in the north and ends at the Third Ring Road in the south, with a Y-shaped main line totaling 19 kilometers. It is built to urban arterial road standards with a design speed of 50 km/h. A 430-meter ground section in the middle divides the tunnel into the East Lake and South Lake sections.

The South Lake section, designed by CCCC Second Highway Consultants Co., Ltd., starts from East Lake in the north, crosses South Lake, and reaches the Third Ring Road. The 8-kilometer main line includes two underground interchanges and four access points to serve group travel.

Comprehensive technical difficulty ranks among the world's top

The South Lake section has a shield diameter of 15.5 meters, currently the largest in China, making it the longest and largest urban underwater lake tunnel in the world.

The head of the design team from CCCC Second Highway Consultants stated that the overall construction conditions of the Two Lakes Tunnel are complex, "no less difficult than building a river-crossing tunnel." The surface features lakes, hills, universities, a national 5A scenic area, cultural relic buildings, and multiple high-rise buildings. Underground, there are highly developed karst areas, full-face hard rock zones, and mixed ground with uneven hardness. The shield tunneling requires crossing under subway lines three times, under urban viaducts twice, and under a railway corridor once. Such conditions are extremely rare for shield tunnels of this scale, and the comprehensive technical difficulty ranks among the world's top.

The design concept of the Two Lakes Tunnel is "build without being seen," fully integrating with higher-level planning, based on the existing road network and greening, focusing on restoring and enhancing the road landscape, blending the landscape into the environment, and hiding the road within the mountains and lakes, making it an organic part of the urban environment. The design follows the principles of adapting to local conditions and ecological conservation, retaining existing plants to the maximum extent while ensuring that the post-renovation landscape integrates organically with the current environment of the connecting sections.

The project starts near the East Lake 5A scenic area, serving as a passage connecting the city and the scenic area. Since this section will be fully renovated and combined with the demolition and reconstruction of Fengguang Village, the design team has designed this section to high standards, making it a waterfront landscape avenue that showcases the city's image. A landscape platform for viewing the lake and mountains is also designed. The landscape design elements echo the East Lake Scenic Area, incorporate the historical and cultural elements of Fengguang Village, and combined with landscape lighting, create a popular waterfront leisure spot at night.

High priority on lake protection and water quality improvement

Nanhu Avenue, nestled between mountains and water, has beautiful scenery and is close to Huazhong Agricultural University, making it suitable for slow traffic. After the project's ramps are connected, new sidewalks and boardwalks will be built to connect the slow traffic system. Based on the flat land filled by the tunnel ventilation tower, an interesting viewing platform will be designed, making it a waterfront landscape avenue that showcases the city's image.

The Third Ring Road section has many exposed loess areas within the red line, and the ecological environment in the interchange area is poor. In the landscape greening design, the principles of large green volume and high coverage are adopted, combined with the "sponge city" concept, terrain is reshaped to store rainwater, aquatic plants and colored-leaf forest belts are planted along the revetment, and rain gardens are created to restore the city's "ecological green lung."

In addition to the engineering construction itself, the project also attaches great importance to lake protection and water quality improvement. In response to the high public concern about lakes, it strictly follows Wuhan's lake management regulations to achieve a "occupy one, return one" balance, ensuring that after the project is completed, the lake capacity and area only increase, not decrease. Furthermore, the project will set up a storage box culvert with a capacity of nearly 50,000 cubic meters under the road along East Lake, intercepting drainage outlets along the route and transporting the water via pumping stations to downstream treatment plants, further improving East Lake's water quality.

On the north shore of South Lake, in conjunction with the South Lake water environment improvement project, a row of DN2200 initial rainwater collection pipes will be built along the tunnel structure boundary on Wenhui Street and Zhuodaoquan South Road to intercept initial rainwater from outfalls along the route. Once completed, it will significantly purify and enhance South Lake's water quality.

It is reported that once the project is completed, it will create a new north-south underground passage in the Wuchang area, alleviating traffic pressure on the eastern section of the Second Ring Road while separating medium- and long-distance through traffic and serving group travel along the route. The project is of great significance with outstanding social benefits, helping Wuhan build itself into a national central city.