Stabilization Of Rock Excavations Using Rock Reinforcement

The use of rock bolts for the support and stabilization of coal mining excavations was introduced over 30 years ago and, since that time, has progressively increased until today it is the primary means of support and stabilization of large underground openings. Early analytical studies and work with photoelastic and physical models established that even highly fragmented rock could be stabilized by rock bolting and form a load-carrying structural member that would span an opening. For stability, interaction of the bolts is essential and it depends on the bolt tension, the length and spacing of the bolts, the characteristics of the rock, and the applied load. However, the development of an explicit functional relationship embracing all these factors proved to be elusive. A review of the early rock bolting investigations led to the concept that the basic element of a rock bolted roof is the reinforced rock unit (RRU), consisting of an individual bolt and the rock immediately surrounding and adjacent to it, and to the development of mathematical equations which give the minimum bolt tension required to ensure that the RRU's are stable relative to one another and act together as a structural member. Analytical procedures have been developed for integrating RRU's into a reinforced rock structural (beam-arch) member which spans an underground opening and providing a rational basis for the design and installation of rock reinforcement systems.