Abstract
Designing support systems for brittle rock masses currently relies heavily on experience, empirical formulations, overly simplified calculations and simulations, and / or trial and error. These approaches result in high uncertainties regarding the support system’s performance and reliability, which directly impacts worker safety (protection against rock falls and rock bursts) and cost evaluations (is the support system too heavy or will it necessitate multiple rehabilitation passes).
With the advent of faster computers, new modeling techniques and a better comprehension of rockmass failure mechanisms, it is now possible to design support systems through numerical simulations. The models allow us to more accurately account for the site-specific conditions prevailing underground which, in turn, results in more reliable designs. This statement especially applies to support systems installed in seismically active environments. The complexity of the interaction between the support elements and the forces applied to them in a dynamic setting, the limited empirical data available and the new hardware continuously being developed to support rockmasses in seismically active mines make numerical models a very compelling tool to use in these situations.
For this paper, the Rigid Block Model in Itasca’s Particle Flow Code was used to design a dynamic support system for a highly stressed pillar. The model uses a zone of bonded rigid blocks around the excavation, coupled with a continuum mesh of finite volume zones (FLAC3D) deeper into the rock mass. This scheme allows the accurate modelling of brittle rock mass failure under low confinement (rigid blocks) and shear failure at higher confinement (zones) in a computationally efficient way. The paper outlines the methodology followed for this study and presents the results obtained for different support designs.