Drilled secant pile construction is a technique used in deep foundation construction of structure. The principle behind this method is to drill several overlapping holes in the ground and fill them with concrete to form a continuous wall of piles.

The process begins by drilling a series of primary piles into the ground, leaving gaps between them. Once the main piles are in place, drill secondary piles in between the main piles, overlapping them. Secondary piles are filled with concrete when drilling to form a continuous pile wall.

This method is often used where soil conditions are challenging or where watertight barriers are required. Overlapping piles provide additional stability and strength to the foundation, making it suitable for supporting heavy structures or resisting lateral forces.