EXOFOR - Foundations

EXOFOR uses the ACP technique - Auger Cast Piles - which is today one of the fastest growing techniques for foundation in the world.

The Continuous Flight Auger method allows the construction of piles with minimal environmental disturbance. It is one of the quietest forms of piling, and is suitable for most types of ground conditions - it is particularly suited to interbedded sequences of clays and sands.

A hollow-stemmed continuous flight auger is rotated into the soil to the required depth using a top-mounted hydraulic motor - no casing is required. A high slump concrete mix is pumped down the stem of the auger and the pile is formed as the concrete is pumped into the pile bore whilst the auger is slowly raised, lifting the spoil on the flights.

Normal pile diameters of 300 mm to 900 mm can be constructed up to a maximum depth of 22.50 m. Depending on ground conditions, working loads of up to 2000 kN can be carried. Reinforcement placed by hand is generally limited to 12 m in depth, but longer reinforcement cages can be installed by vibrator.

As friction piles - the superstructure load is transferred to the soil through friction between the pile surface and the soil.

As an end-bearing pile - the superstructure load is transferred through the pile tip into a hard stratum of soil or rock.

As an anchor pile - hydrostatic or other uplift forces are resisted though a full length tendon embedded in the grout column.

As a vertical component of a continuous auger cast curtain wall in temporary or permanent shoring systems and below grade walls.

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

Advantages :

Less noise.
Auger cast piles are a drilled and pumped pile, not a driven pile.This eliminates the hammer impact noise created by driving piles.

No objectionable vibration.
The elimination of a pile-driving hammer allows the installation of auger cast piles adjacent to existing structures without the danger of settlement or damage to existing footings, walls, other structural components, or nearby equipment.

No casing required.
During the installation of an auger cast pile, the earth filled auger maintains the shape of the pile hole during the drilling phase. The pressures produced by the grout pump during the withdrawal and grouting phase exceed the lateral pressures exerted by the soil, and while the grout is still fluid, the lateral pressures per foot of depth of the grout exceed those pressures per foot of depth of the soil.

Can be installed in limited headroom conditions.
Auger sections can be manufactured to accommodate installation of auger cast piles inside existing buildings with a minimum clearance of 7 to 10 feet. Soil at each pile hole can be inspected. The grout that is pumped into the pile displaces the existing soil for the entire lenght of the pile. This displacing action allows the soil along the lenght to be available for visual inspection and testing.