Double rotary drilling (CCFA)
Procedure of producing a cast-in-place concrete pile with double rotary drilling:
1. Positioning at the drilling point
2. Auger drilling with simultaneous advance of the casing
3. Extraction of auger and casing while concrete is pumped in through hollow stern
4. Inserting the reinforcement
5. Finished pile
Double rotary drilling combines continuous flight auger drilling with a continuous casing. Casing and auger (inside the casing) are simultaneously installed and extracted. Double rotary drilling is applied for the production of cast-in-place piles and for predrilling.