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One of the unique features of the Hydro- hammer® design, besides its sturdiness and high level of controllability, is its ability to facilitate ex- traction of earlier driven casings. A steel tube with a steel cover plate (on the bot- tom) will be driven by a Hydrohammer® with ex- traction cap into the ground until the required penetration depth is reached, or until sufficient resistance to penetration is encountered. Inside the empty tube a reinforcement cage will be placed and concrete will be poured. The Hydro- hammer® with extraction cap will be connected to the tube by link plates, controlled by the pile driver assistant.
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Cast-In-Situ process steps
A steel tube with a steel cover plate (on the bot- tom) will
be driven by a Hydrohammer® with ex- traction cap into the ground until the
required penetration depth is reached, or until sufficient resistance to
penetration is encountered.
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| Cast-In-Situ Technique |
Inside the empty tube a reinforcement cage will be
placed and concrete will be poured. The Hydro- hammer® with extraction cap will
be connected to the tube by link plates, controlled by the pile driver
assistant. Hydrohammer® and tube will be extracted by line pull of the rig in
combination with small blows downwards or upwards of the Hydrohammer® to reduce
the soil frictional resis- tance. The concrete will flow into the soil cavity.
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| Cast-In-Situ Technique |
The required amount of concrete is estimated beforehand. In case of extra
consumption, which can happen in very loose soils, the tube will be refilled
with concrete before being completely extracted to compensate the extra flow
out. A concrete pile of high quality is the result.
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| Cast-In-Situ Technique |
Cast-In-Situ advantages
Fast installation method. High
frequency opera- tion of the hammer with extremely low energy per blow reduces
soil frictional resistance, en- abling pile extraction at crane loads
significantly lower than used for conventional static pulling. Under extremely
difficult circumstances it is even possible to generate an additional upward
force by impacting the hammer housing in an upward direction. This can set a
jammed pile into motion.
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| Cast-In-Situ Technique |
This combination of features means that only one hammer is needed for both driving and extract- ing, making them ideal for handling cast-in-situ (vibro) piles. Economical, since reinforcement is installed after tube installation, compared to pre- cast piles, where reinforcement must be de- signed with respect to transport and handling.
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| Cast-In-Situ Technique |
Concrete can be delivered within a few hours at request by a concrete mixer truck, which pre- vents storage of precast piles and makes it easier to reach the jobsite. Reinforcement of pile shaft can be increased at top of pile.
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| Cast-In-Situ Technique |
Due to an in- creased end bearing and optimal friction along the shaft, a high bearing capacity is usually achieved. Allowable pile loads can be very high. Another advantage is that the adjustable pile length can be determined at the job site.
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