Build a Solid Foundation with Caisson Construction

Learn everything you need to know about caisson construction and how it can benefit your next project

What is Caisson Construction?

Caisson construction is a foundation used in deep water or soft soil. It involves a series of large, watertight cylinders that are sunk into the ground and filled with concrete. The base provides a stable foundation for structures built on top of it.

Bridges, docks, and large structures often use caisson construction. These types of foundations are relatively quick to build. It is, however, essential to ensure the caissons are correctly sealed, as any water leakage can cause significant problems. In addition, caisson construction is typically more cost-effective than other types of foundations.

What are the Benefits of Caisson Drilling?

Here are the distinct benefits of a caisson in constructing buildings.

It is Effective Even in Great Depths

Caisson drilling is an ideal solution if you need to build on unstable ground or very soft soil. This method can create a foundation at any depth, giving you the flexibility to make it just about anywhere.

Construction Costs Are Lower Than With Other Options

Caissons are not only cheaper to install than a massive concrete pad foundation, but also you may be able to skip pile caps since the caissons are already concrete-filled. This cost-effective option can save you tons of money on large construction projects.

It Can Easily Adjust to Its Surroundings

Any worksite can use this construction method. Whether you’re building a high rise in the city or some other large structure in a remote location, caissons will be easy to place.

It Can Support a Lot of Weight

Caisson pillars create a stronger foundation because the weight is distributed evenly across the grid. It helps to bear both axial and lateral loads more efficiently.

Types of Caisson Foundations

There are several types of caisson foundations, each designed for different conditions.

  • Box Caissons – These watertight boxes are created with heavy timbers and lack a top lid. They’re usually floated to where they should be, then sunk into place with the help of a masonry pier inside the box.
  • Excavated Caissons – These caissons are usually cylindrical and placed within an excavated site. A concrete backfill is then applied.
  • Floating Caissons – Prefabricated boxes with cylindrical cavities are also known as floating docks.
  • Open Caissons – Small cofferdams are placed in the water, pumped dry, and filled with concrete. Generally, these are used in the construction of piers.
  • Pneumatic Caissons – Underwater construction uses large watertight boxes or cylinders.

Caisson Construction Process

Here are the steps involved in caisson construction:

  • Once the forms and concrete are in place, the box is floated to the breakwater by a towboat. The caisson guide is then attached to it. Placing concrete in steel forms along the box’s perimeter sinks further into the water as it follows the caisson guide.
  • Air dome forms are built inside the box, and concrete is placed between them. The resulting open tubes above the air domes are called dredge wells.
  • A dredge well is dug after excavating caissons at the riverbed and taking off air domes. Once the caisson hits the river bottom, excavation can begin. The depth of the hole will be determined by how deep the caisson sinks.
  • In the last step, cement is unfilled into the bottom 30 feet of sedimentary wells and then closed off at the top.

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Advantages of Caisson

A caisson foundation has many distinct advantages. The following list contains the primary benefits of using a caisson foundation:

  • Caissons are easily adaptable to many site conditions, making them the perfect solution for construction projects in varied locations. The only tricky part of using caissons is drilling holes for placement.
  • These foundations can easily hold structures that are pretty heavy and also prevent any lateral movement.
  • They are economically viable due to their low drilling and installation costs.
  • As piers are filled with concrete, they significantly reduce the need for pile caps.
  • The caisson foundation will make the house less shaky and less noisy. The foundation is based on piers, which means there will be fewer vibrations that could damage the house.

Disadvantages of Caisson

Although a caisson foundation sounds excellent in theory, there are many more disadvantages to using this type of foundation than traditional foundations. Listed below are the primary cons of a caisson foundation:

  • With few experts skilled in caisson foundations, construction managers and crews often lack knowledge of related procedures and protocols.
  • Since piers entail a lot of drilling, they can’t be placed on sites where the soil is already contaminated. It would only serve to contaminate the area further.
  • Caisson placement is a delicate process, which is why few construction managers are willing to work on projects that require caissons.
  • There’s also a case of caisson disease caused by the bends, affecting construction workers. Caissons must be handled with caution to prevent this disease.
  • Inspection of caisson foundations is rarely done by qualified inspectors, which puts them at risk of being unsafe and insecure.

FAQs About Caisson Construction

Caissons are sturdy, watertight structures made of wood, steel, or reinforced concrete. They are built above ground level and then sunk into the ground. A pile foundation is a deep foundation that uses vertical timber, concrete, or steel to support loads at a low level. Finally, a pier foundation is a deep foundation that uses large cylindrical columns to support oversized loads and transfer them to stable strata below.

Caisson foundations can be as deep as necessary to reach a solid load-bearing stratum. Caisson depth depends on the depth of the water, the type of stratum, and the load to be supported. Most open caissons go as deep as 50 meters, while pneumatic caissons go as deep as 100 meters and are open at the bottom.

Building caissons is not a project you want to tackle yourself—you’ll need to bring in a qualified, experienced contractor. In addition, you’ll need the help of a competent engineer to design the system and inspect the work once it’s finished. The city’s building inspector will also take a look at the completed project.

Caissons are structures built above ground level and then sunk into the earth to support a structure. Usually, they are prefabricated and assembled before being transported. When fabrication and sinking happen simultaneously, it is referred to as well foundation.

Rob Paredes
Article by
Rob Paredes
Rob Paredes is a content contributor for SafetyCulture. He is a content writer who also does copy for websites, sales pages, and landing pages. Rob worked as a financial advisor, a freelance copywriter, and a Network Engineer for more than a decade before joining SafetyCulture. He got interested in writing because of the influence of his friends; aside from writing, he has an interest in personal finance, dogs, and collecting Allen Iverson cards.