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ABSTRACT: Discrete fracture networks (DFN) are applied extensively in the design of underground spaces for both mining and civil infrastructure industries. DFN-based design tools enable discrete modelling of rock masses and kinematic stability assessments to be undertaken for design. When coupled with distinct element modelling, this approach significantly enhances the quality of designs by more precisely predicting the behavior of the ground. This combined approach can identify critical mechanisms, such as block interlocking and unravelling, which are pivotal in controlling the overall behavior of the ground. The paper presents the design method undertaken for a large underground cavern employing DFN models through both static block kinematic assessment and DEM numerical analysis. A comparison of the two approaches highlights the importance of DEM in simulating ground behavior to ensure that critical mechanisms are incorporated into the design. This DFN-based method promotes safer and more efficient designs, leading to improved risk identification and cost savings for the project. 1. INTRODUCTION Discrete fracture networks (DFN) are applied extensively in the design of underground spaces for both mining and civil infrastructure industries. DFN-based design tools are useful as they allow discrete modelling of a rock mass and kinematic stability assessment of individual blocks. When coupled with distinct element modelling (DEM) techniques, the design can be enhanced by more accurately predicting ground behavior, including identifying adverse failure mechanisms that may be critical for the design or interlocking mechanisms that maintain stability of the excavation. The DFN-based design approach to underground space have been successfully applied by authors such as Haryono (2022) and Weir (2018) to predict the range of unstable block sizes for support design. This method enables a real realistic and more efficient designs that lead to better design risk identification as well as cost savings for the project. Block kinematic assessments are a typical first step for rock excavation support design. There are, however, limitations with the method as the approach is usually focused on limit equilibrium and a static block boundary condition preventing the influence of dynamic block interactions (i.e. displacements) from being considered. Impacts of dynamic block interactions may result in interlocking and/or unravelling effects that have important controls on the overall ground behavior.
Ng et al. (Sun,) studied this question.