Secant piles, comprising a solid and robust system, amalgamate earth retention with groundwater barrier walls. Secant pile walls are constructed using a method that involves drilling a series of alternating primary (drilled first) and secondary (drilled second) overlapping shafts. This drilling sequence forms a continuous wall of secant pile shafts. The content of concrete in these shafts can range from being completely low-strength or high-strength or can be an effective combination of the two, with low-strength primary and high-strength secondary shafts. Reinforcing steel or steel piles are normally installed in the secondary shafts. Alternatively, high-strength unreinforced shafts can also be built in a self-sustaining circular structure, akin to those often utilized for access shafts leading to tunnels.
Secant pile walls exhibit considerable impermeability, proving their efficacy in controlling the ingress of groundwater into an excavation and restricting drawdown outside of the excavation. Owing to their stiffness, secant walls are commonly used when there exist structures sensitive to movement behind the wall.
A notable upside of opting for secant piles in cutoff wall construction lies in their compatibility with Schnabel’s high-torque drill rigs. These drills have the capability to penetrate tough drilling conditions, casing the drill hole simultaneously. They are equipped to drive a cased hole through natural and man-made obstructions encompassing cobbles, boulders, and reinforced concrete, providing exemplary secant pile shafts.