Bored Piles are circular piles made of concrete and steel being installed in the soil by various drilling methods. They divert high structural loads into deeper, stronger soils, form stringed together a retaining wall for excavation pits or terraces remove obstacles in the soil or block ground water below the surface. Depending on the application length, diameter, material, formation, and placing of the individual piles can be adapted.
With the Kelly method, uncased, partially cased, fully cased or slurry piles are produced. The drilling tool is fixed to a telescopic Kelly bar. It is drilled step by step into the soil. If fully cased piles are produced, the casings are drilled to the necessary depth and bored until the final depth is reached.
Kelly Method with Bell-Out
Bell-out piles are based on the principle of a circular symmetric extension of diameter at the bottom of the drill hole. The outer load capacity of the pile is increased by enlarging the endbearing area of the pile in the bearing soil layer. The bell-out size is calculated according to structural needs and con-sidering the soil below and the geometrical ultimate criteria. Skin injection is an additional possibility to increase the load capacity. Here, the skin friction of the pile is increased by injecting cement slurry.
Continuous Flight Auger
CFA is a drilling method which enables a high drilling performance in stable soil. A continuous flight auger is used as drilling tool. After having reached the final depth, concrete is injected through the hollow stem auger.
Rotary Twin System
The Rotary Twin System is a combination of CFA with a continuous drilling auger and the Kelly System with casing, which produces a cased drilling according to DIN 4014 / EN 1536 with a continuous auger.
The Front-of-Wall method results from the need to produce new structures directly in front of existing buildings in city centres. The production principle corresponds with the Rotary Twin System, however, smaller diameters are used.