DeWaal Soil Displacement Piles SDP piles, FDP piles, CMC columns

1. Technology behind SDPs, FDPs and CMCs

Installing displacement piles such as Soil Displacement Piles (SDP), Full Displacement Piles (FDP) or Controlled Modulus Columns (CMC) entails drilling a steel tube with a displacement budge which causes soil do be displaced laterally.

The auger for Soil Displacement Piles consist of three sections. The lower auger section, similar to CFA piles, makes it easier to penetrate the soil. The middle section comprises of a displacement bulge which displaces the soil during drilling and retracting the auger. The upper section is a steel drill pipe.

This auger is tipped with a sacrificial shoe which protects its shaft from soil and water penetration. The shoe remains under the toe of the pile after the required depth has been reached.

Concreting SDPs begins once the final depth has been reached. Simultaneously, the concrete mix is pumped and the auger is retracted under clockwise rotation. Structure of the displacement bulge causes a further displacement of the soil preparing an ideal hole for the displacement pile.

After the auger is removed, reinforcement, prefabricated to specification, is inserted into the fluid concrete. The hollow shaft’s large diameter allows for inserting a reinforcement cage prior to concreting, which makes reinforcing long SDPs /FDPs /CMCs much easier.

The main advantages of using SDP, FDP and CMC technologies include

no vibration during installation
more concrete efficient when compared to CFA piles,
compression of the hole side waals during pile installation
increased load bearing capacity using smaller diameter piles (relative to CFA piles)
no spoil during drilling,
speed of installation
clean site.

2. Use of SDPs, FDPs and CMCs

SDPs, FDPs and CMCs are predominantly used in stiff and firm cohesive and medium to dense non-cohesive soils with an Ic index of 0.70. SDP technology can be used in built up areas due to its vibrationless installation. Due to the speed of installation and small diameters of SDPs they are often used in industrial and commercial buildings. SDP technology is an alternative to soil excavation for depths of more than 5 m.