Self-Drilling Anchor Micropile is a kind of minipiles, sometime are called as root piles, are widely used in reinforcement and earth support.
The installation of hollow bat micropile is easy and efficient, thanks to the self-drilling hollow bar anchor combines the processes of drilling and injection in the same operation.
Nowadays in North America and Europe, hollow bar micropiles are widely used in underpinning or emergency repairs.
In these areas, the drilling tools should comply in Europe with DIN 4128, Euro code2 and EN14199/10080 standards and in America with FHWA-NHI-14-007(2015). The steel material of the hollow bar, as well as the thread deformations comply with ASTM F432 and A615.
Right here in the reinforcing steel standards, bending test is required. In the next let’s see the details.
The hollow bar micropile can be bended by a rebar bending tool. The bending test can be easily implemented in construction site.
The bending is around 180⁰ (U-shape) over a pin diameter D ≥ 6x diameter of self-drilling micropile.
For instance, for R32N IBO hollow bar, the pin Diameter = 6 x 32 mm = 192 mm.
After bending, if there are visible cracks or the hollow bar breaks, there is not enough ductility as required in detail in ASTM A615 “Specification for Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement”.
The bending result reflects the ductility performance of a hollow bar micropile. It is intuitive and easy to operate.
For the recent years, the grouting concrete anchor bars are widely applied in micropiles, soil nails, wall tiedown and tieback anchor systems. The self-drilling micropiles with high ductility are reliable protections for civilians in case of earthquake and other disasters happen.