The raising standard of self-drilling anchor hollow bar
The growth of using self-drilling anchor hollow bar in rock bolting, soil nailing and micropiling is rapid.
Self-drilling anchor has been around for at least 40 years.
It is developed for tunneling applications in weak or collapsing ground.
Until today it is still used for the NEW Austrian Tunneling Method (NATM).
However,
Unlike the solid reinforcing bar, criteria for self-drilling hollow bars were not perfect in the past.
Manufacturer had only concerned about loading capacity and surface profile.
You must know solid rebar is required to achieve specific strength, while maintaining excellent ductility.
Ductility means deformations without breaking, plastic, visible deformation until rupture.
It is an important index in construction, represents the safety factor of structure.
Similarly,
Reinforcing is the core function of self-drilling anchor hollow bars, enough elongation ductility should be required.
That's why now you can find elongation Agt is introduced in the latest version of DSI DYWI Hollow Bar Drill Rod Manual, Orica MAI SDA self-drilling anchors catalogue, and ISCHEBECK Titan Hollow Bar Requirement, etc.
Now you can get a checklist for the reference of choosing a standard self-drilling anchor hollow bar:
1. Yield load of finished hollow bar
2. Ultimate load of finished hollow bar
3. Elongation Agt (ductility) up to ultimate without reduction in cross-section of finished hollow bar
So what should you ask suppliers to provide?
Tips:
1. Test reports from independent laboratories. For instance, SGS.
2. Test results include Stress/Strain Diagram, tensile strength and elongation Agt
3. Bended sample of self-drilling anchor hollow bar.
All the information is outlined in detail in the report which is given by ontonbolt. A leading manufacturer of self-drilling hollow bars, used for strengthening the grounds.