Secant Pile Walls
What are Secant Pile Walls?
Secant Pile Walls are formed by constructing intersecting reinforced concrete piles. The secant piles are reinforced with either steel rebar or with steel beams and are constructed by augering. Primary piles are installed first with secondary piles constructed in between primary piles once the latter gain sufficient strength. Pile overlap is typically in the order of 8 cm. Secant pile walls are constructed when resistance to groundwater is required using the CFA technique or the cased CFA technology.
What are Secant Pile Walls for?
Secant Pile Walls are usually installed as retaining structures and support systems for deep foundations, retaining elements and at the same time load-bearing walls and deep foundations for engineering constructions (e.g. walls and foundations of underground storeys, stand-alone and framed bridgeheads, etc.).
How are Secant Pile Walls constructed?
Secant Pile Walls can be constructed using the CFA or the CCFA technology, consisting of reinforced piles with the gaps between them filled with:
- Columns made of low-strength material of 1-3 MPa (concrete or mortar, usually with bentonite), spaced approx. 620-670mm for drilling diameter of 470-500mm. This solution ensures resistance to groundwater (temporary support), but does not guarantee permanent water resistance. In order to ensure permanent water resistance, additional liners or sealing agents are required
- Columns having a compressive strength of 10-20 MPa and prolonged binding time (56-day strength instead of 28-day strength), spaced 700-750mm for a drilling diameter of 470-500mm. This solution ensures long-term water resistance, provided that a minimum overlap of 25mm is provided
- Full-strength concrete piles with prolonged binding time, spaced approx. 400mm for a drilling diameter of 500mm. This solution also ensures long-term water resistance and is widely used as a support system for deep excavations with a pile wall constructed on circular plane, since waling beams and/or struts are not required.
What are male and female piles?
The primary piles/columns cast first are called female or soft. The reinforced load bearing piles are drilled to intersect the female piles/columns and are called male or hard.
How about a Cantilever pile wall?
Cantilever pile walls can be used for protecting land faults up to 5m high or, if using anchors or struts, up to 20m high. Secant pile walls allow for protecting land faults up to 5-6m or, if using anchors or struts, up to 25m high. Standard rake of installed pile wall does not exceed 1:75, however, under special monitoring the rake can be reduced to 1:125, and in some cases, even to 1:200 (for secant pile walls made of hard piles and installed using the CCFA technology).
What are the main advantages of a secant pile wall?
- Increased wall stiffness compared to sheet piles.
- Can be installed in difficult ground (cobbles/boulders).
- Less noisy construction.
Who shall I contact about Secant Pile Walls?
For more information about Aarsleff Ground Engineering or to send in your enquiry, call 01636 611140 and speak to a member of our expert team today, or drop us an email