How many times did you wonder by looking at a bridge and its pillars rising deep under the riverbed? How do you think someone worked there? The physics, science that goes into building underwater structures can be amazing because of sheer engineering skills. It is because of engineers from mechanical, geological, and several other departments that they solved the problem of building underwater.
- Building Cofferdams
It is a simple process where engineers drive long piles of concrete and steel deep into the riverbed or waterbed. Then, they start building on top of it. Because water can erode surface building, the foundations must be much deeper, and that is the first law of science.
In terms of geological surveys and engineering, there are more than long pillars. Engineers must build structures that will not flood and keep the workers safe with water around them. Traditionally, cofferdams were part of a bigger construction where they built support pillars for bridges. This also involves a process we know as “dewatering”.
The piles of a cofferdam go deep into the water bead to the specified depth. And, then walls build up around them. This prevents them from collapsing under huge pressure from the water surrounding these hollow structures. These walls also create a hydrostatically balanced structure so that water also does not seep from below. Only then, workers come and start working in this area.
The process of removing water from the structure is called “dewatering”. The term means that after the walls and pillars are in place, the water from inside is [pumped out. Then, space dries up and workers get to go down and start working. Ultimately, a dry workspace is available for a usual working process as if they are working on the land. So, the only challenge is creating the walls in a manner it can withstand the pressure from the water on all sides.
When ships need some repair, engineers will employ cofferdams to create a drydock like space. This is helpful because it can isolate the SHI from the water, and help make repairs. For larger ships, this is a typical process and these drydocks are very huge. For example, when a cruise ship undergoes extension to make it longer, engineers will first construct cofferdams around the ship. They will perform the “dewatering” step as we mentioned above, and then allow workers to operate in the dry space. So, this is a very expensive process.
- Lakes & Oceans
A more useful way engineers and geological surveyors construct drydocks is by taking the natural geography of an area. For example, the edges of rivers and oceans come in handy because they have natural shallow depressions.
Building a Tunnel Underwater
Because these water bodies are challenging, building a tunnel underwater is a serious task. Bridges seem somehow in font before these giant structures. It was in 1818 when a French engineer builds a machine that allowed workers to carry out tasks underwater without worrying about mud or running water ruining their work. Brunel’s Tunnel Shield was a big invention of that time.
Today, after a bit of progress, things are different. From 1825 to 1843, workers sold spend 9 years of time-consuming and back-breaking effort to build the famous underwater tunnel under the river Thames in London, England. It became the first underwater tunnel in the world.
Today, TBMs or tunnel boring machines make working faster and carving tunnels easy. The advancement became the key ingredient for several modern 20th-century success stories. In these TBMs, there is a circular rotating disc with cutters that bore through the earth. Because the machine evacuates the tunnel, the whole machine moves forward slowly and removes dirt. Finally, this allows the creation of dry space to build the walls. France and England made use of 11 such TBMs to build the historical 32-mile tunnel under the English Channel.
In short, the underwater tunnels are some of the biggest and most ambitious projects. There are other names to this like EuroTUnnel or Chunnel. Ted Williams Tunnel was another adventure because it made use of the cut-over-cover method. By sinking steel tubes deep inside the waterbed, they pump out water to create dry space. There 12 giant tubes, inside which the rads were already there, were lowered into the sea. After sinking, cables firmly fixed it to the floor. Because of experimental rock cutting machines, cable laying machines, today engineering is at an advanced stage. They include commercial divers for underwater welding, fixing tubes, making repairs, and so on.
In short, underwater structures pose some of the biggest engineering challenges. But, the methods available for them are fundamental and still very useful. IN the past 200 years since 1825, the Thames Tunnel has become old. But, the impossible unimaginable Transatlantic Tunnel spanning 3100 miles under the ocean could connect New York to London in an hour.