| Pressodrill
The equipment
for carrying out the Presso-drill pile consists of a crane supporting
a leader, on which a rotary head slides. This head is connected to the
top of the casing and applies a rotation (torque). The weight of the rotary
head, added to the weight of the casing, provides the penetration force
required. In some particular cases, in order to increase this force, a
pull-down by cables can be added.
The equipment
for carrying out the Presso-drill pile consists of a crane supporting
a guide-leader where a rotary head slides. This head is connected to the
top of the casing and applies a rotation around its axis.
The weight
of the rotary head added to the weight of the casing ensures the penetration
force required. In some particular cases, in order to increase this force,
a pull-down can be added.
Pile execution
sequence:
- Bottom
plate installation. The casing consists of a large stem auger, in the
shape of a large pipe with an external helical screw. A waterproof bottom
plate seals the auger tip.
- Penetration
into the soil with compacting effect. The auger is screwed into the
soil and penetrates due to the high pull-down force, combined with rotation.
The soil is displaced and compacted around the auger.
- Penetration
completed. Once penetration has been completed, the auger has compressed
the lateral soil. The bottom plate rests on the natural soil without
disturbance or remolding.
- Reinforcement
installation. After rotation is stopped, the reinforcement is lowered
into the casing. The lower ends of the bars are bent towards the pile
center.
- Introducing
the mandrel. A hollow steel mandrel, provided with side holes, is lowered
down to rest on the cage bottom and on the auger bottom plate.
- Concrete
pouring. Both the auger and the mandrel are filled with fluid concrete
under dry conditions.
- Auger
extraction and base preloading. The top of the auger is equipped with
a device, forcing the mandrel to move downward and the auger to move
upward, at a controllable pressure. This force causes auger extraction,
while the reaction force preloads the soil under the pile tip.
- Extraction
phase without rotation. The reinforcement cage is locked to the bottom
plate during auger extraction; the auger is withdrawn in successive
stages. The weight of the concrete column assures a constant pressure
below the auger helical screw; thus the pile shaft is continuous and
of high quality.
- Finished
pile. After the auger is extracted, the mandrel is withdrawn. The pile
bottom rests on the preloaded soil.
The advantages
of the Presso-drill pile:
- Large
diameter, which means high bearing capacity
- Since
it is cased, it is suitable for all kinds of soils
- No shock,
noise or vibration during execution
- Soil compaction
- No excavation
- Pouring
under dry conditions
- Clean
site
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