Displacement piles are a single pass method similar to CFA, but no soil spoils are removed. Instead of removing the soil while drilling, the tool is designed to push the soil, densifying it, and consequently increasing the skin friction of the pile. During the grouting phase, concrete is pumped through the auger simultaneously with the extraction of the auger from the ground, while the concrete flow and pressure is being monitored by a computer. Typical diameters vary from 12in to 24in, to a maximum depth of 110ft. Usually larger machines are required when compared to CFA as this technique requires more torque and crowd force to drill.