CFA Flight Auger (CFA Piling)
In this method the auger stays in the pile bore to the final depth, being withdrawn slowly with the pile spoil whilst concrete is pumped through the hollow auger stem into the pile. As well as in loose or granular soils, CFA may be the only viable solution for noise and vibration sensitive work, and on some restricted access sites.
CFA is the quietest form of piling and is suitable for forming piles in most types of soil, particularly inter- bedded sequences of clays and sands and water bearing cohesion-less strata.
Hole is bored using continuous flight auger sections.
Once founding depth is reached, the previously attached grout or concrete line to the piling rig head is charged with concrete or grout at pressure. Either sand/cement grout or concrete is injected and the auger stem is withdrawn rotating slowly to remove spoil during the process with the void being replaced by concrete/grout.
Prior to the introduction of the reinforcement cage, the spoil arisings are cleared and pile head laitance removed.
Stage 4 / Stage 5
The pile reinforcement cage is lowered and pushed into the fresh concrete/grout down to ground level.