Secant Pile Walls are fashioned by overlapping reinforced concrete piles. The Secant Piles are strengthened with steel beams or steel rebar. Primary Piles are the first to be installed with secondary piles created in between the primary piles once the primary gain adequate strength. Pile overlap is usually in the range of 3 inches (8 cm). In a Tangent Pile Wall, pile overlap does not occur as the piles are constructed flush to surrounding piles.
The main benefits of Secant Pile Walls are improved construction sequence flexibility, a reduced amount of noise, improved wall stiffness in comparison to Sheet Piles, and where the ground is hard and digging is difficult this is an ideal solution. However, with secant piles complete waterproofing is extremely hard to achieve in joints, and verticality tolerances for deep piles can be hard to obtain.