Short note on auger cast concrete piles

Auger Cast Concrete Piles:

Auger cast Piles are a deep foundation element installed by rotating a continuously flighted hollow stem auger into the soil to a specified depth. Concrete or grout is pumped under pressure through the hollow shaft as the auger is slowly withdrawn. The grout pressure and volume must be carefully controlled to construct a continuous pile without defects. Auger rotation is always kept clockwise to promote migration of soil up the auger flight to ensure a continuous uncontaminated concrete or grout column. The resulting concrete or grout column cures and forms an auger cast pile. Reinforcing can be installed while the concrete or grout is still fluid to aid in lateral and tension design forces as required. The finished foundation element resists compressive, uplift, and lateral loads. Auger cast pile diameters range from 12" to 24" (2" increments). Larger elements of 30, 36, and 42 in. have also been installed. minimum spacing of at least 6 times pile diameters center to center for piles installed within 12 hours of each other provided.

There are many ways Auger Cast concrete piles can be used

·         Friction Piles:-The load is transferred to the soil through friction between the pile surface and the soil.

·         Bearing Piles:-The load is transferred through the pile tip into a dense stratum of soil or rock deep below the ground.

·         Combination of Friction and  bearing piles:-The load is transferred through the combination of both friction and bearing piles

·         A series of adjacent Auger cast concrete piles forming a continuous auger cast wall in temporary or permanent shoring systems and below grade walls.

·         Used as a temporary or permanent diagonal tie-back in auger cast curtain walls, beam and lagging walls, and sheet pile walls.

The main advantages of using Auger cast concrete piles is

·         Since Auger Cast concrete piles are drilled and pumped piles rather than driven pile it eliminates hammer impact noise, so it creates less noise

·         The elimination of hammer impact reduce the vibrations without the danger of settlement or damage to existing footings, walls, other structural components.

·         In many situations it offers considerable cost savings.

·         They have very irregular shape and rough surface in most soil conditions , maximizing the friction capacity of the pile.

·         During their installation the auger maintains the shape of the pile hole during the drilling phase and the pressure produced by the head of grout exceed the lateral pressure exerted by soil so no casing is required.

·         It allows the soil along the length of each pile hole to be available for visual inspection and testing.

The most disadvantage of Auger Cast concrete pile is its sensitivity to operator performance, which can lead to a pile of poor integrity or inconsistent quality. Thus the improper use of Auger Cast concrete pile equipment can result in piles containing defects or can cause instability of nearby structures.