Good cooperation and ongoing optimizations key to success

By thinking along with the design right from the tender stage, the manufacturer, together with construction consortium BAAK, was able to achieve significant optimizations in the foundation structures. The Blankenburg connection is also the first project in the Netherlands to be equipped with a new type of slot filling to guarantee the watertightness of the tub at great depth.

ArcelorMittal Projects reviewed the foundation design in close consultation with the construction consortium during the tender phase and sought optimizations. "For example, the initial design assumed longitudinally welded tubular piles for the deepest construction pits because of the required wall thickness of 33 millimeters," says Roel Bijlard, Technical Sales Engineer. "That design was eventually converted to pipes with a spiral welded seam. A challenge, since hot-rolled steel coils, which are used for the production of spiral-seam welded tubular piles are usually produced up to 25.4 millimeters in thickness. However, our coil plant in Bremen is the only plant in the world that can produce coils up to 28 millimeters thick in steel grade X70. That combination brought the desired solution and allowed us to optimize on both weight and price in the project."

Patented lock fillings

The construction pits in which the Holland Tunnel and especially the Maas Delta Tunnel are being built have a considerable depth. "Sheet piling ditches are reasonably watertight, but when excavating from 10 to as much as 28 meters below ground level, as here with the Blankenburg connection, there is quite a bit of water pressure on them," Bijlard knows. "Applying slot fills ensures a watertight pit and a safe situation, and certainly in this case is a more economical alternative to welding up the piling ditches. Up to a depth of 10 meters below ground level, Beltan lock fills are sufficient. The ditches in the shallower sections were executed with this bitumen-based product, a total of about 85 kilometers of Beltan was applied. The locks in the deep sections of the Meuse Delta Tunnel, on the other hand, are fitted with our patented Akila Sealing System. It is an environmentally friendly, high-performance sealing system for steel sheet piles and based on three sealing "strips" made of silane-modified polymers (MS polymers). The more water level difference, the greater the pressure on the lock, the better the lock seals."

Avoiding risks

ArcelorMittal's hot-rolled sheet piles are manufactured from steel scrap. "We no longer extract primary raw materials such as iron ore from the environment and are the only producer in the world with an EPD validated for the Dutch market," Bijlard continued. The sheet piles used on the Blankenburg connection were produced at ArcelorMittal's plant in Luxembourg, where they also feature the Akila Sealing System. "The sheet piles were produced in 2018, transported to a temporary storage location in the Netherlands and delivered in phases from there. This removed the risk of price fluctuation for BAAK. The tubular piles, on the other hand, were produced on demand and partly shipped and partly transported by axle to the project site. Because of the large quantities, we assigned two full-time project managers to manage the delivery. Finally, lock guides were also used to reduce the chances of a sheet pile running out of lock. To check after installation that the sheet piles had indeed not run out of lock, Dixeran lock indicators were installed on the pipes. So not only did we supply the products, but we also participated in the design and implementation. A wonderful job for us as well," Bijlard concludes.

ArcelorMittal Projects provides complete and customized steel foundation solutions worldwide. In-house manufacturing facilities and inventories enable the company to operate flexibly and easily meet the needs of any project.