The SOB method has been an integral part of deep foundation for years; nevertheless, many of the augers available on the market cannot withstand the required torques and tensile forces. LEFFER SOB augers are designed for torques of up to 470 kNm and are available in 600 mm, 900 mm and 1200 mm diameters. 

Pulling forces of up to 900 kN can be accommodated. This ensures safe pullback during concreting and SOB pile foundations of large diameters and at depths of up to 30 m. 

In the SOB continuous flight auger drilling method, the auger is rotated into the ground to its final depth in a single operation. The concrete is conveyed to the concrete outlet at the lower end of the auger via the core barrel, thus producing the in-situ concrete pile as the auger is pulled. The loosening and conveying of soil takes place continuously. 

The auger is equipped with continuous flights over its full length. The support of the borehole wall is provided by the auger flights filled with the drilled material. 

The LEFFER full displacement auger types VV 400, VV 510 and VV 600 enable a cost-effective, environmentally friendly and safe production of in-situ concrete piles in a vibration-free drilling process. A bottom plate at the drill tip of the full displacement auger ensures that the ground to be worked is fully displaced and compacted at the same time. The actual drilling of the borehole is completely eliminated – a dry borehole is produced without excavating the ground. This low-noise and vibration-free drilling method is particularly suitable when the existing water balance must not be disturbed, where soils are contaminated and soil replacement is out of the question, or for construction work where nearby buildings must not be affected by shocks or vibrations. 

In this drilling method, the borehole is drilled to final depth in one operation using the single-pass method. Since the borehole wall is always supported, the risk of ground failure is minimized. During the concreting process, the displacer can be retracted in a clockwise direction. This creates a spiral embossment of the borehole wall, which significantly improves the load-bearing capacity of the pile. With the patented LEFFER pipe connection system, full displacement bored piles can be produced with an inclination of up to 4:1 and torques of up to 450 kNm can be transmitted.