The following pictures are from a wind farm where due to the weak conditions of the subsoil a deep foundation with piles has been necessary, using a technique known as continuous flight augering (CFA).
As you can see, with the same machine we drilled and pumped the concrete in the hole.
A dry hole has been made, without the use of bentonite or others drilling fluids to maintain vertical the walls of the hole: the earth is removed using an Archimedes’ screw, and than concrete is pumped inside the hole, slowing lifting the tool.
The machine uses a manometer to know the pressure used to inject the concrete in every moment: this way, it is possible to detect if there are holes underground.
Then, the reinforcement bars are lifted using a crane and carefully inserted in the hole. Small plastic wheels are positioned at the sides of the steel structure to make easier to lower it in the hole.
When the concrete hardens, after about a week, the head of the piles is removed using drills, leaving the steel bars clean and ready for the construction of the foundation.
April 26, 2012, www.windfarmbop.com