Combi-wall plays an important role in civil engineering, both industry and construction will use combi-walls. In this passage, we are going to talk about the following parts:
What is the Combi-wall?
The advantages of Combi-wall
A Combi-wall is an earth-retaining wall that, as the name suggests, is composed of different types of profiles. Combi walls are put together through interlocking clutches or by installing sheet piles in between the steel piles.
In combi wall, piles acts as the load bearing structure, while sheet piles installed in between make the wall continuous.
Combination sheet pile walls are typically formed by joining a pair of sheet pile sections with regularly spaced king pile patterns and are typically used when regular sheet piles are not strong enough to carry the required loads.
A Combi-wall is a combination of large-diameter steel pipe piles and sheet piles installed to form a retaining wall structure. Pipe piles provide resistance to overturning forces and the steel sheet piles serve as in-fill between the pipes. Combi-walls can be left in place permanently or elements can be extracted and re-used when no longer needed.
The pipe pile portion of a Combi-wall is typically installed as a bored pile which may or may not be backfilled with concrete and reinforcing steel, depending on the application. Sheet piles are installed in the spaces between the pipes with a vibratory hammer and are aligned with pipes using welded interlocking points. Other pile cross-sections such as H-piles can also be combined with sheet piles to form a Combi-wall.
First, the main advantage of this wall is the great stiffness of the whole, which also increases its bearing strength. The Combi-wall is stabilized by installing horizontal struts or anchors (e.g. MV-piles or ground anchors) in the soil behind it.
Second, Combi-walls provide a cost-effective shoring alternative to the secant wall while providing significantly more load bearing capacity than a sheet pile wall.
Besides, Combi-walls are effective in temporary applications as the steel elements can be easily removed and re-used once the structure is no longer needed.
Third, high strength solution combining maximum stability with economical weights
The high inertia of the system results in low deflection values
Increased vertical load bearing capacity
Ability to penetrate very hard ground
High lateral impact resistance
A cost effective solution most commonly used in marine applications where large dredge depths are required between the sea bed and the top of the wall.
Furthermore, for other category of Combi-wall, it has advantages like following:
the Spiral Steel Pipes advantages
• Long length without joints
• Economical compared to LSAW and Seamless Pipes
• Large range of sizes available
• Access to high grade coils
• Provision of corrosion protection before delivery
The King pile wall advantages
• Increased wall stiffness
• Increased wall moment resistance
• Sheet piles can be terminated at higher elevations
• King piles can extend deeper to better bearing strata
• Might offer a better alternative to other systems
• Ideal for heavy marine applications
• King pile wall disadvantages
However, every coin has two sides, Combi-wall also has disadvantages like:
• Increased cost when compared to standard sheet piles
• Installation more complex compared to sheet piles
• Greater coating surface when compared to sheet piles
• Soil must be removed.
• Final water-retaining properties cannot be guaranteed because of the many interconnections of the piles.
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