The design of ground support needs to account for a number of uncertainties relating to loading conditions, rock mass variability, rock mass response and ground support performance. When designing ground support for dynamic conditions, the uncertainties are magnified due to significant gaps in our understanding of how the rock mass responds to dynamic loading as well as limitations in available design methodologies (conceptual uncertainty). In reality, the fundamentals of dynamic ground support design have changed little over the last three decades and there are many assumptions and limitations. This paper will discuss some of these limitations, as well as highlight how uncertainty around significant parameters, such as peak particle velocity and design magnitude, impact on the design. Comparisons will be made on how dynamic ground support design is approached in Australia and South Africa. A case study that demonstrates both our general lack of understanding and how variable the rock mass loading and response can be over a short distance will be presented. Suggestions will be made on how to address some of the shortcomings and uncertainties in the design of ground support for dynamic conditions.
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