introduction of underwater construction

Underwater Construction Techniques:

1. Caissons
2. Cofferdams
3. Underwater Concreting

Placement methods

1. Tremie  
2. Pump method
3. Toggle bags
4. Bag works

In recent times, a new method of caissons : Pneumatic caissons has evolved and has changed the future of underwater constructing drastically.

Pneumatic caissons are sunk into the sea floor and have pressurized air pumped in from the surface. These watertight retaining structures structures allow us to build at great depths and enormous pressure levels. Used for work on bridge piers, dams, and ship repairs, this innovative yet dangerous technique helped to create the Ends Bridge piers in St. Louis. This was the first bridge to use pneumatic caissons in pier construction and these are still some of the deepest caissons ever sunk. The Eads Bridge was completed in 1874 and these caissons inspired John Roeblings’ work on the Brooklyn Bridge, which was completed nearly a decade later.

Suction Dredgers is another one such technique that has evolved with the times to make underwater construction a paradise.

Sometimes known simply as dredges, these are machines or vessels that move material from a body of water using a tube and suction method. Various dredging methods exist, but when it comes to breaking up gravel and bedrock, the best are CSDs or cutter-suction dredges, which use cutting tools at the suction inlet. Other types of dredges use grabbing methods such as the clamshell, and some use dragging techniques to move the earth. The amount of uses for this machine make it the Swiss Army knife of underwater construction techniques. Land reclamation, seabed mining, and flood prevention are just a few projects that put dredges to use.

Immersed tube tunnels are another type of structures used in underwater construction.

Composed of separate elements, the underwater tunnel’s parts are sunk in place then assembled beneath the water. Pieces are prefabricated and often sealed so they can float to the location and then link together. Because of the speed at which they can be joined, this technique became the most cost effective and efficient way to create underwater highways and train rails ever since the Michigan Central Railway Tunnel ran one under the Detroit River in 1910. They do come with maintenance issues, especially at their joints which need extra waterproofing and constant attention.

OffShore Oil Drilling is one of the most complex and influential construction projects on earth. 

Deep sea oil drilling happens at depths of as much as 8,000 feet thanks to technical advances that boggle the mind. Compared to the first submerged oil drilling off of freshwater platforms in the late nineteenth century, today’s deep sea oil drilling looks like something from outer space.

Ten types of platform and rig systems exist, including some that float and those that are fully submersible. It can take two years just to assemble the platform and rig even with new technologies being implemented at every phase. But once in place these machines become steel mountains of industrial science. Routine techniques in use today include 3-D seismic imaging, horizontal drilling, and enhanced oil recovery processes that bring 5 to 75% more crude oil from an oil field. With so many uses for crude oil these massive projects affect everyone on the planet.

Commercial divers must be multi-faceted in their training, and are required to perform under extreme and inhospitable conditions.

An integral skill for any commercial diver is to have a firm understanding of the principles of underwater construction and how this type of construction is utilized.

For instance, divers are often employed to weld on underwater structures - including pipelines, dams, bridge piers, and retaining walls - and the diver must be knowledgeable about the underwater construction techniques and tools which contribute to the creation and maintenance of these underwater structures.

Oftentimes, commercial divers will employ a variety of specialty tools such as underwater saws, torches, and welding rods, to repair and maintain a variety of underwater structures such as the ones listed above.

As with traditional construction done above water, safety is a top priority in marine construction. Divers must communicate closely with topside on the status of the task at hand so that both parties can operate efficiently and safely.

Underwater inspection is also a vital component to underwater construction. Divers must be able to survey the condition of existing structures and relay this information to topside. Divers are often outfitted with underwater cameras to provide valuable information which can be analyzed after the inspection has been completed. Remotely controlled submersible vessels may also be used to inspect structures when circumstances call for such measures to be taken.

Underwater construction is utilized by the US Navy, city and state governments, as well as private diving companies to carry out a variety of tasks pertaining to underwater infrastructure. Whether it be construction or repair, chances are commercial divers will be the ones to help carry out the task at hand.