SSAB - steel micropiles
Our Team has had a meeting with Antti Perälä, who works in SSAB - a leading company for steel micropiles.
SSAB was formed in 1978 in Sweden and now 2014 RUUKKI is a part of it. Together they create a Nordic and US-based steel company, which is a leading producer on the global
market for Advanced High Strength Steels (AHSS) and Quenched & Tempered
steels (Q&T), standard strip, plate and tubular products as well as
construction solutions.
The company has
employees in 50 countries and 5 divisions:
- SSAB Special Steel
- SSAB Europe
- SSAB Americas
- Tibnor
- Ruukki Construction - Leading European provider of energy-efficient building and construction solutions.
One of its important challenges is sustainability, because manufacturing steel costs a lot of energy and has a big impact on the environment. For
example about micropiles, SSAB wants to use more AHSS which allows to use less
steel to achieve the same capacity. In fact the Advanced High Strength Steel has special features as a high yield
(max. 550 MPa) and tensile strength (max. 760 MPa). The piles’ load bearing
capacity can be added by 25%, decreasing the number of the piles that you need
to use.
DRIVEN RR MICROPILES
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RR piles are micropiles that
consist of a longitudinally welded steel pipe, an external or internal friction
splice, a pile tip and a bearing plate. They are installed by
impact driving or jacking.
The special feature is that there
aren’t any joints, but they use only friction.
During the installation, if the micropile is not long enough, the first part of
it can be driven into the ground, then the second one can be added on the top and
they can be pushed all together, no welding no screwing. This is possible because there is a splice
that holds the parts together. Moreover material and money can be saved because
it’s possible to cut a micropile and use the remaining part in the next one.
The pros of these micropiles
are: quick and cost-effective splicing, minor displacement of soil, minor
vibration disturbance and high installation strength.
DRILLED RD MICROPILES
RD
micropiles are installed for drilling in difficult ground and environmental
conditions. They can be made as long as you want as the piles can be screwed
together. Because the piles need to be screwed together it is not possible to
reuse the pieces that have been cut off at the end of the pile. In this way
more of the product is gone to waist. As
with the other piles the screw top and the thread is pre-made in to the pile.
The
piles can be installed to a great depth and can be drilled through all natural
soil layers all the way into the bedrock.
This can be done with small deviations in position and inclination.
The RD
drilled pile is high strength micropile and is there for sustainable by
reducing the number of piles. As explained earlier in this article.
PILE WALL
RD pile
walls are suitable for retaining wall structures in difficult ground
conditions. Through interlocks (see picture) the piles are connected. This
interlock makes sure that when the piles moves they will not unlock and ensures the water
tightness of the bottom of the pile without separate injection pipes.
The RD
pile wall works best if retaining wall structures that are under not only
horizontal loads but also vertical loads, as the wall can take both forces. The
ring bit that is used to drill the wall in is oversized as the attachments for
the piles have to be drilled in as well. Some of these ring bits can be folded
in and out making it possible to revive them for later use.
Geoteko award 2012
The Finnish
Geotechnical Society (SGY) has selected Ruukki’s RD pile wall as an outstanding
geotechnical achievement, representing the gigh degree of Finnish geotechnical
expertise. The wall is easy to install all the way done to the bedrock,
eliminating many of the technical risks involved in traditional retaining
walls.
Trondheim
This
wall has been used in the construction of the Trondheim road tunnel, which is
part of the E6 road project that has started a few years ago. The reason this
wall was chosen is because of the soil at the site that consists of very easily
disturbed quick clay, as the pile wall can be applied for vibration-sensitive
strucres. The retaining wall must be installed with minimum stress to the soil,
all the way down to the bedrock. Of the 500m tunnel 120m have been furnished
with drilled pile walls.
The
article about the pile wall in Trondheim and other news can be found on the
Ruukki.com website.
CE-MARKING
The CE
marking is written on all Ruukki’s products. This means the products are performing
well according to European standards making it possible to ship them across
Europe and the world. Ensuring health, safety and environmental protection.
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