Steel Pipe Application: Combi-Wall

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Piling walls used in heavy marine construction and deep foundation applications often require high bearing capacity and stiffness. In instances where a regular sheet pile wall will not suffice, a combined sheet pile wall, also known as a “combi-wall” system, can be used.

Combi-walls are walls created using a mix of steel pipe and sheet pile. They can be temporary or permanent, and they’re a good alternative to traditional retaining wall structures such as secants or sheet pile walls.

Combi-Wall Installation

Combi-walls are built using large steel pipe and sheet piles. The steel pipe provides the bulk of the wall’s structure, while the sheet pile is used to fill in spaces between the pipes, making the wall continuous.

The steel pipe used to construct a combi-wall must be stable, heavy, rigid and straight to create a strong frame. Similarly, when installed, extreme care must be taken to ensure that the pipes are embedded straight and vertical, which will guarantee that they are parallel to each other and allow the wall to retain its integrity.

Combi-wall steel pipes are typically installed as bored pile, which is sometimes backfilled with concrete and reinforcing steel, depending on the application. A vibratory hammer is then used to install sheet pile into the spaces between the pipes. Finally, the sheet pile is aligned and welded to the pipes at interlocking points.

Combi-walls are built to be either temporary or permanent. In the case of temporary combi-walls, their elements can be deconstructed and reused later when the wall is no longer needed.

Combi-Wall Applications

Combi-walls are often used in place of secant or sheet pile walls. They’re typically seen in heavy marine construction and deep foundation projects where the piling wall must have a high bearing capacity and a regular sheet pile wall will not suffice. Some common combi-wall applications include:

  • Retaining wall structures
  • Building foundations
  • Wharves
  • Piers
  • Roadway structures
  • Railway structures
  • Bridges
  • Dams
  • Lake filling
  • Port expansion

Combi-Wall Advantages

Combi-walls provide a number of advantages. They have significantly more load bearing capacity than a sheet pile wall, meaning they can be used for larger projects. They’re also a cost-effective shoring alternative to the secant wall, making them a more economical option.

Combi-Walls and Steel Pipe

Combi-walls are constructed using steel pipe for a number of reasons. High-grade steel has excellent bending stiffness and resistance, creating a more reliable wall. Unlike other metals, steel will bend rather than break in extreme conditions, which means it’s less likely to crack or leak. Similarly, the strength of steel makes it a great option for combi-walls since it can withstand vibrations, shock and high pressure.

Steel pipe is rust-resistant. Unlike other metals, steel pipe is long lasting and resistant to many chemical reactions that cause corrosion. For permanent combi-walls, steel pipe is low maintenance and will last long beyond its installation.

Steel pipe is easy to install. The metal can be customized to any height, width or strength, and it can be modified on site as needed. Because of this, steel pipe is considered one of the most versatile and convenient types of pipe to use.

Finally, steel pipe has a high capacity. It’s stronger than most other types of metal and can be made larger or thinner without compromising its durability. In combi-wall construction, this durability is what makes steel pipe a necessary choice. To learn more about steel pipe, check out our blog titled "All About Steel Pipe".

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