Self-Drilling Anchors (SDAs) are hollow core rockbolts which serve as both the drill string during drilling of a support hole, and as the support tendon once grouted into place. A single use drill bit, selected to suit the ground condition, is fitted to the leading end of the SDA with a plate and nut fitted on the trailing end. Couplers can be used to combine SDA sections for extension bolting.
Hollow core bolts (HC Bolts) utilise the same hollow bar as SDAs but are supplied without a drill bit for applications where a convetional drill string can be used to drill the support hole. Once the HC Bolt is inserted into the pre-drilled support hole, resin or grout is injected through the bolt to complete the installation.