Large-Diameter Steel Screw-Piles
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| NKK's large- diameter steel screw-pile for building foundations |
NKK has obtained certification from the Land, Infrastructure and Transport Ministry for its new large-diameter steel screw-piles designed for tall building foundations based on Japan's new Building Standards Act.
Measuring 1,200mm in diameter, the new product is an enlarged version of NKK's previously marketed steel screw-piles having a maximum diameter of 508mm. The pipe's larger size is useful for foundations of large 10-20 story structures, while conventional piles of this type have mainly been targeted at medium-to-tall buildings some 3-8 stories high.
The steel screw-pile features two wing-shaped semi-circular plates fitted crosswise on the pipe bottom. The screw-like wing section permits easy, eco-friendly driving without removing any soil, leading to reduced installation costs. Because the area of the wing section is larger than the pipe itself, greater bearing capacity is ensured, making the product equal to or better than competitive concrete piles. And unlike concrete piles, there is no need to use cement milk, eliminating worry of ground water contamination.
To enhance the bearing capacity of the new 1,200mm-diameter screw pile, the steel pipe thickness was increased to a maximum 25mm from an 18mm maximum seen in conventional piles. The intersection angle of the two wing plates was also doubled to 28 degrees to make the pile easier to insert into the ground. The pile can be driven to a maximum depth of 60m by rotating the shaft with an auger.
NKK's steel screw-piles have been widely used in medium high-rise buildings thanks to earth-friendly, economical installation procedures, achieving an annual supply volume of 10,000 tons. With the new certification for larger-diameter piles, the company plans to increase production by 50% to 15,000 tons this fiscal year, aiming at 50,000 tons annually within 3-5 years.
