Rock reinforcement and ground control are key issues in underground excavation.
One scope of research, which is in particular of interest for underground tunnelling,are self-drilling hollow bar systems. In the past decades, substantial technical advances in the development and design of these systems have been accomplished. On the basis of some practical examples, this manuscript illustrates the development and successful application of self-drilling rock reinforcement systems.
The main features of all hollow bar anchors and rock bolts are the application of a single-use drill bit in combination with the anchor rod being used as a drill steel. Thus,the anchor or rock bolt is connected to the hydraulic rock drill by an adapter device and installed in the way a conventional borehole is drilled.
The self-drilling installation of the bolts is accomplished similar to the drilling of a conventional borehole; the hollow anchor bar is connected to the shank adapter via a coupling and is being utilized as
3 drill steel; the single-use drill bit is put at the top of the hollow bar. In case where larger bolt lengths are required, the anchor bars can easily be extended by couplings.
