Secant pile wall formation is accomplished by the construction of intersecting reinforced concrete piles. When making secant pile walls, stabilizing reinforced steel bars or beams are introduced. These are constructed either by underwater auger or beneath mud surfaces. Initially, primary piles are constructed and inserted. The secondary piles are introduced later, intertwined with primary piling when the bond is deemed to be strong enough. There is generally a pile overlap of approximately three inches (8 centimeters) in most applications. Tangent pile walls differ in that there is no overlap. With tangent pile walls the inserted reinforcing mediums are aligned at exact points that fit perfectly next to one another.
There are several advantages to using secant pile walls. There is markedly improved construction alignment stability and is far superior in wall stiffening when compared with sheet piles. The pile walls can be installed in difficult terrain, such as cobbles, stones and even boulders. Disadvantages are increased cost when compared with sheet pile walls. There also may be difficulties with waterproofing specific points and verticality tolerances may be harder to achieve. Weaker concrete is used when reinforcing with steel beams into the secant pile walls. Sheer and compression arching may sometimes occur when using steel beams so the lagging piles in between the two main beams and the wall must be examined regularly.
Tangent pile walls have the advantage of no overlap of the reinforcing steel and are meant to have no one pile touching another. This variation allows for increased efficiency of construction alignment and stability and generally easier construction overall. A prime disadvantage is that the tangent pile walls can not be utilized in areas with high water tables. A de-watering process would be needed in such circumstances.