Secant piles form part of a dependable and firm system that merges earth retention and groundwater barrier walls. The process of secant pile wall construction incorporates drilling a series of primary (drilled first) and secondary (drilled second) overlapping shafts in an alternate pattern to shape a continuous wall. Concrete in the shafts can either comprise only low-strength, only high-strength, or be a mix of low-strength primary and high-strength secondary types. Secondary shafts commonly house steel piles or reinforcing steel. Unreinforced high-strength shafts can additionally be fashioned into a freestanding circular ring, an option often chosen for tunnel access shafts.
Secant pile walls, being relatively impermeable, are an effective tool for managing groundwater flow into an excavation and restricting drainage outside. Additionally, due to their rigidity, secant walls are the preferred option when sensitive structures are located behind the wall.
A key advantage in choosing secant piles for building cutoff walls is the capacity of Schnabel’s high-torque drill rigs to penetrate tough drilling conditions while casing the drill hole. These drills are capable of advancing a cased hole through both human-made and natural blockages, including cobbles, boulders, and reinforced concrete.