Civil Engineering Reference
In-Depth Information
Figure 3.16
Auger Rig with Kelly bar drive. (Photograph courtesy of Bachy-Soletanche.)
crane is generally necessary for handling temporary casing, boring equipment, etc.
Some specially developed rigs, usually for the smaller diameter piles, can handle boring
tools and casing from a second winch line running in a double cathead.
The usual crane-mounted auger will bore to a diameter of at least 3000mm. Depths
of boring vary fromaround 25m from cased auger rigs to as much as 60m for the larger
crane-based auger rigs, with telescopic, triple extension Kelly bars. Typical design loads
vary from 1000 to 20 000 kN, in suitable ground conditions. Although the auger rigs
can bore raked piles at up to 1:3.5 (more usually 1 in 4), it is considered better practice
to take lateral and inclined loads on a suitably reinforced vertical pile of sufficient
cross-section.
The augers fitted to this type of rig are usually of the 'short' flight type for large
diameters. Alternatively, in ground that breaks up excessively after cutting, a bottom-
opening toothed bucket may be used. Both augers and buckets can be equipped with
hardened teeth for breaking up lightly cemented deposits. A slight, if irregular, increase
in bore diameter can be obtained using reaming cutters attached to the periphery of
the auger. Various items of auger equipment are illustrated in Figure 3.18.
