How Engineers Make Underwater Construction Make Possible?

Hello, welcome back to theconstruxtor.com. In today’s blog article we’re talking about the most dangerous civil engineering’s most challenging task, “underwater construction” and different types of underwater construction techniques and engineering.

Water bodies are a major part of the landscape. Oceans, rivers and Lakes are often beautiful but they are not necessarily convenient places to build things. Most of our tools and construction materials, not to mention our labour force, work better in the dry. So when there’s a need to build structure under the water, underwater construction techniques and engineering comes to make this possible with experienced engineers and professionals. One of the major costs of large construction projects on or near water bodies is how to manage that water.

Table of Contents

What is Underwater Construction?

Underwater construction refers to the process of building, repairing or maintaining structure below the surface of water bodies such as lake, rivers, oceans etc. Underwater structures comes under wide range of projects including offshore oil rig and gas platforms, underwater pipelines, submarine cables, underwater tunnels, bridges, dams, marine research facilities, and marine habitats. It serves various purposes including resource extraction, infrastructure development, environmental protection, scientific research, defense and tourism.

Today, underwater construction can be accomplished by divers but professional diving is dangerous and the types of tools and equipment that can both function underwater and be safely used by divers are fairly limited. Remote underwater vehicles and other types of submersible equipment are a modern alternative but they are expensive and are limited in what they can do. At the end, it is not possible to build mega structure without removing the existing water.

Challenges of Underwater Construction :-

There are many undefined challenges comes when we work beneath the water, here are some of the key challenges faced by Engineers while working :-

Pressure : All we know that as we go deep under the water, pressure increases. This pressure can affect both equipment and labourers so we need safety precautions to prevent accidents.
Visibility : Poor visibility underwater can make it difficult to work, increasing the risk of errors and issues. Bright lighting and sonar technology can benefit to reduce this challenges.
Current and Tides : Water current and tides can make difficult because of movement of equipment and the stability of the structure. Proper planning and management can execute the work safely and effectively successful.
Corrosion : Exposure to saltwater also accelerate corrosion of materials used in underwater construction, reducing their lifespan and structural integrity. Anticorrosion coating is necessary to mitigate this risk and ensure the longevity of the structure.
Access & Mobility : It becomes a quiet challenging to access the working site to getting personnel and equipments. Divers may need to ensure safety before getting there, sometimes Remotely Operated Vehicles and Autonomous Underwater Vehicles can be used for tasks that are dangerous or deep for human divers.

How to Do Underwater Construction?

A lot of underwater construction actually involves getting rid of the water so we are not building under it at all. In the industry, this is called “dewatering” or sometimes just “care of water” and it includes a wide variety of construction equipments and techniques that all have a single goal in mind to allow construction to happen safely and soundly in areas that would otherwise be infeasible or impossible to build because of water. The heart of many site’s dewatering plan is the Cofferdam, a usually temporary structure built to hold water back from the construction site.

Cofferdam :-

Cofferdam is a temporary structure built to enclose an area underwater for dry work place to carried out the construction work. It is commonly used to create a dry workplace by pumping out the water inside the enclosed area. In many cases, this is simply an earthen berm. We can just dumb soil into the water and delete creation embankment tall enough to serve impoundment. Once your construction area is enclosed we can simply pump the water out.

Of course violet some watch permeable so we need to constantly pump out the water that manage is to seep through. Although the uncompacted and saturated soil is not very strong. A collapse could be extremely dangerous for any workers below the cofferdam so these types of structure requires careful design by an engineer in charge to make sure they are safe.

If you want to learn more about cofferdam visually you can check out the below link.

How are underwater structure built?

Other types of Cofferdam :-

Besides the earthen berm, there are a huge variety of cofferdam designs used on construction sites. Some use sheet piles, thick steel plates that interlock together. These are driven into the subsurface soils using a huge hammer to create a watertight barrier to the subsoil of the bed rock.

If the soils are too rocky to drive sheet piles, or the depth is very high, sometimes sheet piles are used to create small individual enclosed which are hollow in between and then this hollow space is filled with soil called cellular cofferdam.

There are also cofferdam built of steel frames with a membrane and even water filled rubber bags. No matter what they are made from, cofferdams are almost always built to be dismantled and removed after construction. One important use of cofferdam is to build actual bridge. In this case often two cofferdams are necessary to block of the river on the upstream and downstream ends.

For certain types of structures, the foundation can be constructed off side and floated in by barge, commonly called a caisson. A hollow box or cylinder is lowered into its proper location and then the soil is excavated and removed from within the area until a hard strata of rock bottom or strong soil is reached. Finally, the caisson is filled with concrete.

Concreting for Underwater Construction :-

Once dewatering is done we can start working under the dry conditions but sometimes the water particals are traveling in a u shape below the cofferdam. This is because of the water partial difference and this thing happened in cofferdam when we remove water from that. The seepage water control processes is very different thus we should pump water out continuously. If the soil above the hard strata is removed and concreting is done than half of the work is done, this is called the concrete seal course technique. This course also act as a strong footing preventing any water seepage. Piles also penetrated into the bedrock through vibrating hammer machine can help seal course to bond with the bedrock.

It’s time to tackle the remaining construction work, the water seepage is efficiently blocked by this structure. The high quality reinforced bars to be placed for the foundation of the bridge pier or any other work. Engineers ensure that the material used for the underwater construction are of the best quality, they must succeed successfully bear the water pressure as well as the load coming out from the superstructure. After checking all the shuttering work and steel work, progressing arrangement are made to pour concrete in the structure, once the concrete is completely poured into the skeleton, this structure remained undisturbed to gain required strength for the 14 to 28 days.

The cofferdam is of no use and it’s time to remove it with important safety majors. The sheet piles can be cut through from the bedrock and other shuttering work can be removed safely from the cofferdam. Once the shuttering work and cofferdam is dismantled, the structure is ready to take the load and the further work above the superstructure can be done to complete the construction projects.

How do Engineers make Underwater Construction?