Portuguese 
Spanish 
Chinese underwater highway draws attention for the scale of the pieces used at the bottom of Dalian Bay, where colossal concrete tubes were positioned in a maritime environment to create an express crossing hidden under the water and directly connected to urban mobility.
Under Dalian Bay, in northeast China, an underwater highway was built with 18 giant concrete tubes, pieces about 180 meters long and weighing approximately 60 thousand tons each.
Installed using the immersed tunnel method, these structures form a six-lane underwater passage that crosses the bay and connects urban areas previously separated by a much longer land route.
The Dalian Bay Undersea Tunnel is 5.1 kilometers long and was designed to significantly reduce travel time between the two sides of the bay, according to information from the China Communications Construction Company, CCCC.
-
Massive Transporters Otto and Lore Move ALMA Radio Telescope in Chile’s Atacama Desert
-
Singapore Turns Incinerated Waste Ash into Construction “Sand” in Ambitious Project to Revolutionize Megacity Waste Management
-
Brazilian Entrepreneur Turns Passion for Amazonian Cocoa into a Million-Real Chocolate Business After Studying in France
-
Structural Report Reveals Serious Issues at Historic Corinthians Stadium, Engineer Recommends Partial Demolition
In practice, a journey that could take about an hour by land routes is now completed in approximately five minutes through the tunnel, transforming a natural barrier into a fast urban mobility route.
Giant concrete tubes were sunk into the sea to form the tunnel
The most impressive aspect of the project is the method used to assemble the structure, as the tunnel was not simply excavated beneath the seabed as in bored projects.
In this system, large sections are manufactured away from the final installation point, transported by water, positioned over a prepared trench on the seabed, and connected one by one to form the underwater corridor.
Due to their dimensions and mass, each tube functions as a colossal piece of infrastructure, with a length exceeding that of many urban buildings and a weight comparable to large vessels.
According to CCCC, the immersed section of the tunnel totals 3,035 meters and comprises 18 tubular segments, in addition to a final joint used to complete the connection between the submerged sections and the land parts.
The installation operation requires high precision because each module needs to be fitted in a submerged environment, where currents, water pressure, and operational limitations make positioning much more complex.
In the case of Dalian, the final joint received special attention from the construction company for using a sectional advancement method considered unprecedented in the country for this application, with installation control on a millimetric scale.
Immersed tunnel in Dalian Bay became a landmark of Chinese maritime engineering
Besides the size of the pieces, the project draws attention for being executed in a cold climate and high latitude region, a condition that increases the challenges of immersed tunnels in a maritime environment.
For CCCC, the project represents the first major immersed transmarine tunnel in northern China, with technical expertise aimed at new applications in coastal areas with similar characteristics.
Designed as a dual carriageway urban expressway, the tunnel has three lanes in each direction and a design speed of 60 kilometers per hour, integrating road transport and maritime infrastructure.
The main structure has a projected lifespan of 100 years, according to the construction company, a period that reinforces the strategic role of the connection for Dalian’s mobility and for the connection between areas north and south of the bay.
In the port city of Liaoning province, the underwater passage reorganizes part of the urban flow by creating a direct route under the water, without relying on longer paths around the bay.
This new connection offers a rapid transit axis between residential, commercial, and industrial areas, regions that previously relied on longer routes to overcome the separation imposed by the local geography.
Installation on the seabed required millimetric scale precision
Before the arrival of the tubes, the seabed needs specific preparation to support the weight of the structures, an essential step to ensure stability to the set after installation.
After this submerged base, the modules are guided to the planned point, sunk in a coordinated manner, and connected to the previous sections until the sequence gradually forms the tunnel through which vehicles pass.
The scale of the pieces helps explain the visual impact of the project, as a single segment of 180 meters and 60 thousand tons depends on specialized manufacturing, maritime transport, and high-precision submerged operation.
When the 18 tubes are aligned on the bay’s bed, the set creates a kind of highway fitted on the seabed, invisible to those observing only the water’s surface.
According to CCCC, the project accumulated dozens of patents and technical results during its execution, including advances related to precision control, adaptation to the cold maritime environment, and experience with large-scale immersed tunnels.
Among the points highlighted by the company are the final stage of connection, the coordination of underwater operations, and the accumulated learning from previous projects that also used prefabricated structures in an aquatic environment.
Dalian Submarine Highway Links Urban Transport and Coastal Engineering
For the driver, the experience boils down to the tunnel entrance, the illuminated track, and the quick crossing under the bay, without direct contact with the complexity hidden beneath the asphalt.
Behind this everyday passage, however, lies a chain of reinforced concrete, naval planning, positioning equipment, and geotechnical knowledge, essential elements to transform giant modules into a continuous route.
The choice of the immersed tunnel method is linked to the need to cross an aquatic area without building a bridge over the bay, preserving maritime navigation on the surface.
This solution creates a protected passage under the seabed and keeps vessel traffic free, a relevant feature in port regions where road transport and maritime operations coexist in close spaces.
Dalian has a strong port and industrial presence, making mobility between different areas of the bay a sensitive point for urban functioning and the integration of economic zones.
By adding a high-capacity route in an underwater environment, the project brings maritime infrastructure, road displacement, and urban development closer in a region where these sectors intersect directly.
Submarine Megastructure Transforms Dalian Bay into Road Corridor
The contrast between the daily use of the road and its submerged complexity makes the tunnel especially curious, as the crossing lasts only a few minutes, although it depends on giant pieces sunk in the sea.
Beneath the track used by vehicles, there remain 18 colossal structures that were manufactured, transported, submerged, and connected at the bottom of Dalian Bay to create a continuous path.
With this project, transport engineering occupies an area previously treated as a natural barrier within the coastal city, converting the bay’s bottom into an active part of the road network.
By transforming the submerged environment into a road corridor, the Dalian Bay Undersea Tunnel brings together concrete, navigation, geotechnics, and urban operation in a structure that remains invisible to those who only observe the sea.
If 60,000-ton tubes can already form a highway beneath Dalian Bay, what will be the limit of the next megastructures that countries will still sink into the sea?
