Geotechnical Engineer Shares Secrets Behind Building Tunnels and Bridges Underwater

The construction of underwater tunnels and bridges is done with the intention of improving traffic conditions and making driving more convenient for motorists. On the other hand, how are underwater bridges and tunnels constructed? In this article, a geotechnical engineer reveals the secrets that lie behind the building of these structures.

(Photo : Pexels/Masood Aslami )

Underground Construction

The geotechnical engineer Ari Perez, who is also an assistant professor of civil engineering at Quinnipiac University, stated that the process of constructing underwater is a challenging and complicated endeavor. However, engineers have invented a number of methods to construct underwater, frequently by not constructing underwater at all.

Most of the time, strong tunnel-boring equipment is utilized in underground construction to extract the earth directly. The machine is frequently referred to as a mole for a certain purpose. It excavates horizontally into the ground, much like the animal does, and then removes the material that it has excavated out behind it. This creates a tunnel that is comparable to a burrow.

Moreover, when executed with caution, this technique has the potential to successfully construct a tunnel through the ground beneath a body of water, which can subsequently be lined and reinforced afterward. Through the use of this technique, engineers were able to construct the Chunnel, which is a railway tunnel located beneath the English Channel that connects France and England.

Nevertheless, as the tunnel continued to expand, new transitory structures were constructed at ever-greater depths. The shields were later developed into the current tunnel-boring machine based on the fact that they were constructed to be moveable as the designs improved with experience.

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Challenges With Water

Construction that takes place underground is both hazardous and difficult to access. There are additional complications that come with dealing with water. Even though it is possible to construct a stable aperture by moving soil and rock aside, water will always move in to fill any breach, and it is necessary to pump water out of the area regularly.

Also, it is often impossible for people to construct things underwater; therefore, there are two choices available: either construct the building in the open and then relocate it underwater or temporarily change the submerged site into a dry one. Accordingly, crews will typically construct the structure on dry land, and then they will sink the components into place.

The Ted Williams Tunnel in Boston, for example, was built in parts within a shipyard from the beginning. The path that the tunnel would eventually take across Boston Harbor was excavated by workers, and mud and other debris were removed. Once the trench was ready, they proceeded to position the portions that had been sealed.

In addition, following the completion of the segment connection, the ends of the segments were opened in order to produce a single, continuous tubing that was quite long. When it was finally finished, the tunnel was covered with rock and earth. In reality, just a small portion of the construction process was carried out underwater.

As an alternative, construction workers can construct directly from the surface in some circumstances, such as when the water is shallow. Instead of needing to redirect the water, for instance, workers can drive sheet metal retaining walls into the ground straight from a barge. These walls are used in shoreline areas.

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