Secant Pile Wall Features

Secant piles are constructed in such a way that they intersect each other. These piles are commonly used in excavation support systems (such as soldier piles, nailing, anchorage, and top-down methods) where the spacing between piles is less than their diameter. The secant pile wall is particularly effective for controlling groundwater flow and minimizing soil movement in soft, saturated ground conditions.

Three Construction Types of Secant Piles

  • Hard/Soft Secant Piles

  • Hard/Firm Secant Piles

  • Hard/Hard Secant Piles

In these systems, the gaps between piles are filled with unreinforced materials like cement-bentonite slurry (in hard/soft) or weak concrete (in hard/firm). For hard/hard configurations, all piles are cast with high-strength reinforced concrete.

The construction process typically begins with primary piles, followed by secondary piles that are reinforced and intersect with the primary ones. This overlapping ensures continuity and water-tightness. The diameter of these piles usually ranges from 500 to 1200 mm.

Secant pile walls are stronger than tangent pile walls and offer superior groundwater cut-off performance during deep excavations.

Figure 1. Secant piles used in excavation stabilization
(Excavation stabilization using retaining structures, nailing, anchorage, top-down method, etc.)

Tangent Pile Walls

Tangent piles are another type of cast-in-place pile used for excavation support, where piles are constructed side-by-side in direct contact without overlap. Due to the lack of intersection, they provide less resistance against groundwater seepage compared to secant piles.

Figure 2. Tangent piles used in excavation stabilization
(Excavation stabilization using retaining structures, nailing, anchorage, top-down method, etc.