An Investigation of the Factors Controlling the Mechanical Behaviour of Slender Naturally Fractured Pillars
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ORIGINAL PAPER
An Investigation of the Factors Controlling the Mechanical Behaviour of Slender Naturally Fractured Pillars Ladan Karimi Sharif1 · Davide Elmo1 · Doug Stead2 Received: 3 August 2019 / Accepted: 11 July 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Previous studies on the strength and deformability of pillars in hard-rock mines have demonstrated that the influence of natural fractures diminishes with increasing pillar width. Jointing conditions and fracture intensity/intersections play a critical role in the behaviour of slender pillars (width-to-height ratio less than 0.5). An important challenge is the characterization of rock mass damage as a function of the natural fracture network and loading conditions. In this paper, we present advanced pre-processing methodologies to measure fracture intensity and fracture density prior to loading and relate those measures to the evolution of damage (intensity and density) with increasing pillar load. A hybrid finite-discrete element method (FDEM) with fracture mechanics capabilities is used to simulate the mechanical behaviour of synthetic pillar models with different embedded discrete fracture traces of similar total length. Newly developed post-processing methodologies are used to capture the location of damage events, track rock mass damage intensity and density as the simulation progresses and relate those changes to the modelled pillar strength. We believe the results of this study provide useful insights on rock mass damage evolution. Keywords Discrete fracture network · Finite-discrete element modelling · Structural damage · Brittle damage · Dilation · Block characterization
1 Introduction Previous studies on the strength and deformability of pillars in hard-rock mines have demonstrated that the influence of natural fractures diminishes with increasing pillar width (Esterhuizen et al. 2011; Elmo and Stead 2010). Jointing conditions and fracture intensity/intersections play a critical role in the behaviour of slender pillars (width-to-height ratio less than 0.5). An important challenge is the characterization of the rock mass damage as a function of the natural fracture network and loading conditions. In this paper, advanced preand post-processing methods are used to integrate brittle failure and degree of natural rock mass blockiness using a combined discrete fracture network (DFN) and hybrid finite-discrete element method (FDEM) modelling approach.
* Ladan Karimi Sharif [email protected] 1
University of British Columbia, Vancouver, BC, Canada
Resource Geotechnics Research Group, Simon Fraser University, Burnaby, Canada
2
Whereas the method is primarily targeted at FDEM models, it could also be applied to DEM models in which a Voronoi/ Trigon tessellation approach is used to simulate fracturing processes (Gao and Stead 2014). In the literature, several authors (e.g. Elmo 2006; Esterhuizen 2006; Esterhuizen et al. 2011) have argued that the strength of slender pillars is highly variable and dependent on the
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