SPECIALIZED PILING

While driven steel pipe piles are common for deep foundations, specific site conditions—such as restricted access, environmental noise sensitivity, or retaining wall requirements—demand specialized methods. Below are three common alternatives.

---

1. Steel Sheet Piling

Applications: Retaining walls, cofferdams, and bulkheads.

Sheet piling consists of long structural steel sections with a vertical interlocking system. Unlike load-bearing pipe piles which support weight from above, sheet piles are driven edge-to-edge to form a continuous wall that resists lateral (side-to-side) soil or water pressure.

2. Continuous Flight Auger (CFA)

Applications: Environmental and noise-sensitive sites.

Also known as Auger Cast Piles, this method is ideal for urban areas where the vibration of a driving hammer is prohibited. It is a cast-in-place method:

1. Drilling: A hollow-stemmed continuous flight auger is rotated into the ground to the required depth. No casing is required as the earth-filled auger supports the bore hole.
2. Concreting: A high slump concrete mix is pumped down the hollow stem of the auger.
3. Withdrawal: As the concrete is pumped, the auger is slowly withdrawn, removing the soil and leaving a shaft of fluid concrete to ground level.

3. Tripod Piling

Applications: Restricted access and difficult ground conditions.

The tripod rig is one of the more traditional piling methods. Although unit costs are usually higher than modern rotary rigs, it has several advantages that ensure its continued use:

• Small Footprint: Can work in extremely confined spaces (like backyards or inside buildings).
• Versatility: Can drive a casing through boulders or difficult strata that might stop other rigs.