Improving bench design through discrete fracture network analysis

Authors: Valerio, M; Rogers, S; Lawrence, KP; Byrne, C; Veltin, K; Darakijan, T; Gaida, M; Cambio, D; Chapin, GK Download Paper

DOI https://doi.org/10.36487/ACG_repo/2135_29

Cite As:
Valerio, M, Rogers, S, Lawrence, KP, Byrne, C, Veltin, K, Darakijan, T, Gaida, M, Cambio, D & Chapin, GK 2021, 'Improving bench design through discrete fracture network analysis', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 457-472, https://doi.org/10.36487/ACG_repo/2135_29



Abstract:
Discrete fracture network (DFN) analysis methods can assist in our understanding of bench-scale slope performance in open pit mines and provide results that are more representative of structural conditions compared to conventional kinematic methods. Conventional kinematic analysis may not adequately capture the complexity of the fracture network and its impact on bench-scale stability because this method is typically limited to analysis of simple rock blocks or wedges formed by one or two fracture sets only. This simplification of block geometries, combined with the limitation of not adequately representing variations in the location and spacing of discontinuities forming blocks, can result in significant differences between theoretical and observed bench performance. DFN methods provide an alternative approach to conventional kinematic methods to model the structural fabric. The fracture networks developed through DFN modelling incorporate variations in the location, spacing, and persistence of discontinuities. DFN-based approaches allow more detailed analysis of the probability of occurrence, probability of failure, and expected back-break when compared to conventional kinematic methods as wedge geometries are more explicitly defined from observed features. This paper provides a comparison between conventional kinematic analysis and a DFN-based approach to bench design, with a focus on back-break metrics for two case studies: one slope governed by potential planar instability and a second where potential wedge failure is the controlling mechanism. The impact of mining processes and time-dependent rock mass degradation on observed back-break is discussed. Comparison between the results of both conventional kinematic and DFN methods to actual bench performance observed at the Bingham Canyon Mine indicates that the DFN approach can deliver results that are more structurally representative of field conditions.

Keywords: bench design, discrete fracture network, kinematic analysis, back-break, bench performance

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