1. Bored Piles
Production Method
Bilfinger Berger Spezialtiefbau GmbH
Goldsteinstrasse 114
D-60528 Frankfurt
Phone: +49-69 6688-345
Fax: +49-69 6688-277
Email: spezialtiefbau@civil.bilfinger.com
www.foundation-engineering.bilfingerberger.com

2. Large Diameter Bored Piles Pont de Normandie
Large bored piles are used as foundation elements to carry
concentrated building loads into deeper, more stable soil layers.
Furthermore, they can be utilized as piles for retaining walls if there Maumee River Crossing
is not enough space for flat foundation.
In the same way, retaining walls for excavation pits are constructed
by using multiple bored piles as bored pile wall, which later can be
incorporated into the final building.
Bored piles can be easily adapted to the various load and soil
requirements due to the large variety in diameter and construction
techniques. Single pile diameter can vary between 30 and 300 cm.
Piles can be constructed in all kinds of soil condition.
In contrast to driven piles, bored piles enable the immediate In-situ
evaluation of drilled soil layers to revise foundation length due to
changed soil conditions.

3. The specific pile construction method depends on the soil condition, Bridge L71 across the Heilsau
the ground water elevations, site conditions and the length of the
pile.
Construction methods can be distinguished between Pont de Normandie
• The bore hole stabilization process during excavation Fully
cased, partial cased, uncased and fluid stabilized excavation can
be distinguished Lilla Bommen Tunnel
• The method of installing the casing
Here one can distinguish between driving the casing with a free
fall hammer or weight, vibrating the casing, pneumatic installation
or hydraulic installation with the help of a rotary drive, an oscillator
or rotator.
• The method of excavation
Here one can distinguish between grab excavation, rotary drilling,
airlifting, and flush boring.

4. Bore Hole Stabilization High Speed Rail Nürnberg -
Ingolstadt, Tunnel Offenbau
Uncased bore holes can only be excavated in stable soil layers. In
general a short starter casing is been used at the pile top.
If uncased excavations run through unstable soil layers, the bore Center for Innovative Medicine,
hole wall has to be stabilized by fluid overpressure. Water or Hamburg
bentonite as well as polymer suspension is used as stabilizing
fluid.
Partially cased bore holes are cased in areas with unstable soils Gallileo Tower, Frankfurt
and deeper and stable soil layers are stabilized by water, bentonite
or polymers, while rock layers do not require any support.
The casing of the borehole has to stabilize the soil and minimize
the relaxation of the surrounding ground. It is always required
whenever unstable soil layers cannot be stabilized with fluids and
there is a risk of soil caving.
CFA piles (Continuous Flight Auger) are drilled uncased by the use
of a continuous hollow auger stem. Stabilization of the borehole
wall during excavation is provided by the soil filled auger. During
pulling of the auger stem, concrete is pumped through the stem,
preventing any soil instability of the bore hole wall.

5. Methods of casing installation Driving by vibratory hammer
During casing installation, tip resistance and skin friction of the
casing has to be overcome.
Installation by free fall weight Driving by free fall weight
Casings in single length up to 6 m are installed using a fee fall
weight. Suitable soil conditions are required for such driving
practice. During this installation method, casings with extra collars Free wall weight
will be driven, excavated and so-called Jumbo piles are
constructed.
Installation by vibratory hammer
Casings are installed into the ground using externally induced
vibration. Friction between casing and surrounding soil is reduced
by vibration generated from an attached vibro hammer. The casing
penetrates the ground due to this vibration, the weight of the
hammer and its own weight. This installation method has a limited
use due to the soil densification inside the casing and possible
vibration damage on adjacent buildings or structures.

6. Pneumatic installation by the HW method HW principle
The HW-method, named after Hochstrasser/Weise, uses a
pneumatically-driven swinging arm, sitting on top of the casing, to
drive the casing in a horizontal back and forth movement. End HW swinging arm
stops transfer the rotation impulse of the swinging arm into the
casing, which rotates slightly at each stroke. This considerably
reduces the skin friction between soil and casing. The casing is
excavation by the wire rope guided grab at the same time. Dike rehabilitation Emmerich
The casing is driven into the ground as a result of the reduced skin
friction and under the weight of the casing and swinging arm.
A major advantage of this method is that the excavating crane does
not have to be placed right next to the casing to support the
reaction forces from the swinging movements of the equipment.
The HW unit can therefore be utilized as a separate unit from the
excavating crane, which is an advantage when piles need to be
installed in steep slopes or over water.

7. Hydraulic casing installation Rotary drilling rig, Galeria
Kaufhof, Alexanderplatz, Berlin
The hydraulic installation method uses an oscillating motion
(Oscillator) or a continuously rotating motion (Rotary Drive or
Rotator) of the casing to reduce the skin friction between casing
and soil. Rotator (RDM)
All of these machines also induce a vertical downward force into the
casing, which in combination with the casing’s own weight enables
penetration of the casing.
Oscillator (VRM)
The casing normally consists of separate sections, which are
connected and bolted during installation.
During the casing installation, the excavating equipment is always
placed right next to the casing and receives the reaction forces from
the rotary motion.

8. The Method of Excavation HW – Grab, long version with
parallel shells
Grab Excavation
Excavation using a free fall or spherical grab is mostly used when
boreholes are very deep and other methods come to their limits or Ball grab with spherical shells
in combination with the HW method.
The borehole is advanced using grabs consisting of a base body,
the grab shells and the closing mechanism for the shells. One
Flat chisel
distinguishes between single-rope and double-rope operated grabs.
The single-rope grab also uses the lifting rope as a closing rope for
the grab shells. The double-rope grab is used with two ropes, one
for grab lifting and one for closing the shells. Ring chisel
Performance of the grab mainly depends on the correct shell
shape, which is chosen according to soil parameters.
For excavations below the groundwater level, in-the-wet drilling
tools such as gravel pumps or mud cans are available for the
various drilling diameters.
Free-fall chisels are used to drill through large obstructions such as
bricks, boulders or rock layers as well as for the pile penetration
into bedrock. Various sizes and shapes such as cross, flat, stellar,
ring shapes are available. These chisels are equipped with different
blades depending on the various soil properties.

9. Rotary drilling methods Sketch - drilling rig
During the rotary drilling method, the excavation is advanced using
drilling augers and buckets.
The drilling rig consists of a base carrier and the drilling unit Drilling rig with bucket
mounted on top of the carrier. One distinguishes between short
augers and continuous flight augers.
When drilling with short augers or buckets, the torque and Drilling rig with continuous auger
downward crowd is transferred to the drilling tools via a telescopic
drilling rod (Kelly bar). Drilling and discharging of the excavated
material are alternating operations, which are performed in a swift
order. Depending on soil conditions and pile diameter, various
augers are used. For excavations below the ground water level,
drilling or digging buckets are used. Obstructions or rock layers can
be removed with the help of core barrels. To increase the pile base
area, belling buckets or under-reamers can be employed.
When drilling with continuous flight augers, the auger is
connected directly with the rotary drive without an intermediate
drilling rod and is rotated into the ground for its full length. After
reaching final drilling depth, the filled auger is pulled out of the bore
hole. Therefore the empty bore hole has to be stable enough or
concrete needs to be pumped through the hollow auger stem
immediately. Pile length is limited by the length of the auger and the
size of the drilling rig.

10. Flush drilling / wet drilling methods Sketch air-lifting drilling method
for bored pile construction
In contrast to the dry drilling method, where the soil is loosened and
excavated by the drilling tools, the wet drilling method only uses
drilling tools to loosen the material and requires a flushing stream
for transportation. Cutting tools like tri-cone bits, roller bits or Air-lifting drilling method
under-reamers are used.
When using the direct flushing method, bentonite or polymer
suspension is pumped down to the piles tip through the hollow
drilling rod. The suspension is then raised up to the piles top in the
annulus between drilling rod and bore hole wall. This method is
most suitable for smaller bore hole diameters.
When using the reversed circulation method, the flushing
suspension is poured directly into the bore hole. Using a vacuum
pump, the soil/suspension mixture is then sucked through the
drilling rods to the pile’s top. Pile length up to 50 m can be drilled
efficiently.
The air-lifting method also pours flushing suspension directly into
the bore hole. By inducing compressed air into the lower end of the
drilling rod below the water level, the expanding air creates an
upward flow, which therefore transports the soil/suspension mixture
to the top of the pile.
Combinations of air-lifting and reversed circulation drilling can drill
bore holes up to 150 m depth efficiently, depending on soil
conditions.