Dynamic rock support in burst-prone rock masses

Rockburst occurs in hard and strong rock after excavation when the in situ rock stresses are high. The "driving force" for rockburst is the energy released from the rock mass. The released strain and seismic energy is transformed to the kinetic energy of rock ejection during rockburst. To prevent out-of-controlled rock ejection, the released energy has to be absorbed by the rock support system when a rockburst event occurs. Therefore, it is required in dynamic rock support design that the support elements must be capable of absorbing a good amount of energy in burst-prone rock conditions. On the other hand, it is required that the displacement of the tunnel wall must be neither larger than the ultimate displacement capacity of the support elements nor the maximum allowable operational displacement. The types of rockburst, the dynamic loading conditions, the design principles of dynamic rock support, and typical yield rockbolts used for combating rockburst issues are presented in the paper.