With self-drilling hollow bars there are significant benefits in respect of installation cost and drilling time in certain ground conditions and as the system is ideally suited to loose overburden drilling their use has become widespread in recent years. The self-drilling technique combines the placement of reinforcement and grouting in a single pass, without the need for a casing in ground conditions where boreholes are prone to collapse.

Typically installed with rotary percussion drilling, using the simultaneous drill and grout technique where grout is pumped through the bore of the bar to the sacrificial drill bit as drilling is advanced with the grout flush comprising a part injection / part flush system. Permeation of grout beyond the nominal borehole diameter can occur in granular soils but be very limited or non-existent in cohesive soils. Air flush, with very careful flush control, has been used in cohesive soil;

May be constructed with cased or un-cased drilling systems to form the borehole into which the anchor components (either bar or strand) are inserted and grouted in place;

Have a defined free length which is isolated from the ground and is free to extend elastically when the anchor is stressed and then throughout its working life;