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Drilling with bored pile grab is one of the oldest dry drilling methods and is still common today. Depending on the tools used, e.g. bored pile grab, chisel or special tools hanging on a duty cycle crawler crane, the soil is loosened either by cutting or impact driving. This method is applied, for instance, for well drilling with small drilling diameter or for the production of cast-in-place piles with sometimes very large diameters.
1. Insertion of the casings
2. Emptying of the casings, e.g. with bored pile grab
3. Inserting the reinforcement
4. Concreting and step by step extraction of the casing
5. Finished pile
The video shows duty cycle crawler cranes from Liebherr in drilling operation with hammer grab at various construction sites.
Drilling with bored pile grab can be applied in nearly all types of soil, with or without groundwater.
For drilling with bored pile grab duty cycle crawler cranes of the HS series are used as carrier machines.
The bored pile grab penetrates the ground in free fall and loosens it with a combined deformation and shear movement.
The digging grab is positioned at the bottom of the borehole. The ground is loosened by closing the spherical shells.
Cased boreholes are always recommended when the building ground is not stable enough.
Mainly casing oscillators, type VRM, are used for drilling with bored pile grab.
For difficult soil conditions or long casing sections, casing rotators, type RDM, are used.
Compared with rotary drilling rigs, boreholes can be installed with a larger distance between carrier machine and drilling axis.
After the final drilling depth has been reached, the reinforcement cage is inserted and, subsequently, concrete is filled in.
For drilling operations with restricted headroom, special short booms and drilling tools are available.