Understanding continuum and discontinuum models of rock-support interaction for excavations undergoing stress-induced spalling

Abstract

Although the design of underground structures is becoming increasingly dependent on modeling-based analysis approaches, ground control systems continue to be designed primarily using a site-specific trial and error approach. This discrepancy is related to the difficulty of reproducing rock-support interaction behavior in its entirety using commonly applied modeling methods. To help bridge this gap, this study has conducted a comparison of continuum and discontinuum models with a focus on their ability to realistically capture the support effect generated by rock bolts with or without wire mesh. It was found that continuum models can adequately replicate the damage processes and deformation of reinforced rockmasses, but show a negligible change in ground behavior when support elements are explicitly considered within the models. We propose a ‘strain-continuity’ hypothesis where the inability of the modeling method to allow discrete block separation after failure is thought to be responsible for this unrealistic behavior. Two discontinuum bonded-block modeling approaches (Voronoi Tessellation and Trigon) were subsequently tested; realistic behavioral differences between the supported and unsupported model conditions that are consistent with empirical data were exhibited by the Voronoi model. Finally, a conceptual framework has been presented that combines field data from the literature with the modeling results to provide an understanding of how support responses in the continuum and discontinuum models compare to reality.