Similar to contiguous piling, secant piles are spaced at regular intervals but overlap one another, typically by 150mm. This overlap ensures a degree of water-tightness and secures against soil particles migrating through the retaining wall.
Secant walls can take the form of different configurations:
Hard-Soft:
Soft piles use a weak concrete or concrete/bentonite mix that is easily cored through with the piling rig. Hard piles use structural concrete and are reinforced with steel elements. Hard piles extend to a full depth to provide a structural support, and soft piles may only extend nominally below a retained face.
Hard-Hard:
As above but each pile uses structural concrete and typically all piles are reinforced.
A guide-wall is constructed to ensure that positional and vertical tolerances can be maintained and provide confidence that a regular and even overlap is maintained.
Suttles use a range of techniques that include CFA, cased CFA (CCFA) and rotary boring to construct the piles. Suttles are capable of installing pile diameters ranging from 300mm up to 1200mm and depths of 26m.
