A probabilistic evaluation of the displacement-based ground support design approach

Abstract

This paper describes the use of Monte Carlo simulations to perform a probabilistic evaluation of the displacement-based dynamic ground support design methodology used to determine the dynamic ground support requirements for hard rock and brittle behaviour in a high stress environment such as Cadia East. The design approach uses several probabilistic inputs including stress level, depth of strainbursting, bulking time, pre-existing bolt head displacement, rock mass bulking, and peak ground velocity. The main mechanism under consideration is the dynamically loaded strainburst where a remote seismic event triggers a strainburst at an excavation. Several of the inputs are represented as probabilistic distributions to capture the variability and uncertainties within each parameter. The outputs are represented as probabilities of having Factor of Safety less than one for the specific support designs assessed. The methodology defines the acceptance criteria of a given ground support profile based on the layers of protection assessment. An example is detailed where three dynamic ground support systems are assessed for an undercut drill drive using the method.