Rock support is the term widely used to describe the procedures and materials used to improve the stability and maintain the load bearing capacity of rock near to the boundaries of an underground excavation. In this paper, a distinction is drawn between rock reinforcement or active support, where the supporting elements are an integral part of the reinforced rock mass, and rock support or passive support, where the supporting members are external to the rock and respond to inward movement of the rock surrounding the excavation. A good example of active reinforcement is a pattern of untensioned grouted dowels which are tensioned as the rock deforms and which interact with the rock in much the same way as reinforcing steel does with concrete. Steel sets are an example of passive support since they external to the rock mass and can only respond to progressive inward movement of the loosened rock mass.
The primary objective of a support system is to mobilize and conserve the inherent strength of the rock mass so that it becomes self-supporting. Rock support generally combines the effects of reinforcement, by such elements as dowels, tensioned rock bolts and cables, and support, with shotcrete, mesh and steel sets which carry loads from individual rock blocks isolated by structural discontinuities or zones of loosened rock. These notes are intended to assist the underground support engineer in choosing the most appropriate, and the easiest to install, combination of reinforcement and support. If possible, the installation of rock support should be carried out as an integral part of the excavation cycle to enhance the self -supporting aspects of rock mass improvement.