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

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.