Bored Piles

Bored piles are cylindrical concrete structures (with or without reinforcement) that are inserted into the ground using various methods. They transfer high structural loads into deeper load-bearing soil strata, form a supporting wall for an excavation pit or topographical change or seal off groundwater when tangenting or intersected. The length, diameter, material, configuration and arrangement of the bearing piles can be modified according to the intended use.

Types of Construction Method

The Kelly method is used to produce uncased, partially cased, fully cased or slurry-supported bored piles. The drilling tool is attached to a telescopic Kelly bar and the  soil is gradually removed from the casing. The drill casing is continuously bored into the soil which is extracted until the final depth is reached.

Twin rotary system is a combination of the CFA method using a continuous flight auger with the Kelly method with drill casing, resulting in a cased bore hole, produced by using a continuous flight auger (TRS 620, 880 mm). This method is particularly advantageous in the case of high groundwater and uplift-prone soil layers, which would call for drilling under water load with the Kelly method.

The CFA method is a high-performance rotary drilling tech-nique (CFA 630, 750, 880 mm). In this process, a continuous flight auger is implemented as drilling tool. Upon reaching the final depth, concrete is fed in from the bottom to the top through the core barrel of the hollow stem auger. The retaining structure is installed retrospectively, with vibration assistance if necessary.

Compared to the CFA method, the FDP system has the distinct advantage that hardly any cuttings are brought to the surface. This method is employed in displaceable soils. The drill string comprises an auger starter, the displacement body and an extension pipe. When drilling out and extracting, the existing soil is displaced. The concreting and reinforcing steps are performed in the same way as the CFA pile.


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