Secant piles are bored pile retaining walls that consist of a system of reinforced concrete piles that are placed in an overlapping manner in terms of their positioning. This overlapping avoids the possibility of gaps between the adjacent units.
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Secant Pile Casted Image Courtesy:Â cordek.com |
Secant piles are one of the techniques developed to allow the construction of the wall within the ground prior to the full excavation of the basement void. These structures create a perimeter retaining wall, around the basement areas, to safely excavate the soil. These are permanent embedded retaining walls.
Construction of Secant Piles - Secant Piling Procedure
Arrangement of Primary and Secondary Piles in Secant Wall Construction Image Credits:Â www.geotech.hr |
Secant Pile Design Considerations
- Hard/Soft
- Hard/FirmÂ
- Hard/Hard
Hard/Soft Primary Secant Pile |
Hard/Firm Primary Secant Pile |
Hard/Hard Primary Secant Pile |
The primary pile uses a soft cement-bentonite
mix of strength  (typically 1 N/mm2), i.e.
unreinforced. |
Primary pile uses a weak mix concrete or full-strength concrete of strength
10 N/mm2 |
High-strength concrete is used. They can be reinforced. |
Do not provide full water-tightness |
Used where permanent works, reinforced concrete lining is demanded |
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Applications of Secant Pile Construction
- Slope stabilization works
- Providing supports for excavations
- Providing supports for bulk-head
- Provide water cut off to conduct excavation
- As cut-off barriers
- Retaining walls against liquefaction, in hard soil, in sloped areas.
Advantages of Secant Pile Wall Construction
- Cost-effective option for short-term water retention
- Provide greater pile wall stiffness compared to sheet piles
- Can be constructed in areas with low headroom and difficult ground conditions
- Have increased construction alignment flexibility
- No requirement for installing timber lagging
- The construction is less noisy
- Less vibration during construction, hence less deformation and settlement on the outside
- Can carry high loads from the surrounding structure
Disadvantages of Secant Pile Walls
- The total waterproofing between the joints is difficult to achieve
- The cost of construction is higher compared to sheet pile walls
- The verticality tolerance of deep steel helical piles is less compared to sheet pile walls.