Combined walls - steel tubes and sheet piles

Combined walls with steel tubes are an alternative to the HZ-M/AZ system. Tubular piles are the main retaining elements of the combined wall (king piles), carrying horizontal loads from soil and water pressures and vertical loads from the superstructure or anchoring system. The intermediary AZ sheet piles (infill sheets) transfer the horizontal loads from the retained soil and water to the tubular piles. Note that infill sheet piles are usually shorter than the king piles.



In some countries, U-type or cold formed steel sheet piles are used as infill sheets. ArcelorMittal does not recommend to use double or triple U-piles as infill sheets because of their reduced rotation capacity (interlocks are located on the neutral axis). Cold formed sheet piles have a looser and weaker interlock shape, so that ArcelorMittal does not recommend them as infill sheets.

One advantage of steel tubes is that they can be built-up from the same outside diameter tubes, but with different thicknesses over the length in order to adapt the resistance of the piles to the variable moments along the height. This solution is however only economically viable for rather long steel tubes because of the cost of butt-welding.

The main disadvantage of large diameter tubes is shipping (high cubage factor) and the weight of a single element to be driven (may require quite powerful driving equipment).

Buckling and torsion of relatively slender tubes may be a concern for high strength steels. A European project has studied these complex phenomenon for foundation piles and the results have been published a few years ago.

Tubular piles from ArcelorMittal are available in numerous European and US steel grades (large number of own facilities producing coils). The piles are provided with C9 connectors, which guarantees the minimum interlock hook connection (see EAU 2012), and can be coated on request.

ArcelorMittal Commercial RPS supplies spirally welded tubular piles manufactured in ArcelorMittal Projects’ mill in Dintelmond (NL). Tubes are delivered with EN 10204 - 2004 certification. The Dutch mill is equipped with a deep-water quay and can export tubular foundation piles with diameters up to 3000 mm, wall thicknesses up to 25 mm, and lengths up to 49 m without butt-welding.

The table below gives an overview of some of the possible combined wall systems. Please refer to our brochure “Spirally welded steel pipes” for further details.