Secant (Caisson Walls)
Secant or Caisson Walls, also known as drilled concrete pile walls, are created by first drilling primary piles at a specific spacing and backfilling with concrete. Secondary piles, sometimes called soldier piles, are then drilled in between the primary piles such that they overlap by a specified amount, drilling out part of the concrete from the primary piles on each side before backfilling with concrete. The result is a continuous wall of concrete piles known as a Secant Wall. Additional reinforcement may be provided by inserting steel section or rebar cage within the secondary piles. Tie-back anchors and walers can be installed to provide added stability.
- While secant walls can be more costly than other shoring solutions, they offer greater wall stiffness and minimal movement which can be critical for some projects.
- Different installation methods can be used to achieve secant walls depending on site and ground conditions, enabling construction in difficult soils and limited overhead room.