Authors: Guajardo, C; Jakubec, J; Esterhuizen, E; Pichuante, H; Thomas, A

Open access courtesy of:


Cite As:
Guajardo, C, Jakubec, J, Esterhuizen, E, Pichuante, H & Thomas, A 2022, 'The Discrete Fracture Network–Block Caving Fragmentation hybrid method: A new tool to assess fragmentation of block caving mining projects', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 927-938,

Download citation as:   ris   bibtex   endnote   text   Zotero

The forecast of the size distribution of the fragmented rock, in the form as it will report at the drawpoints, is one of the relevant aspects to be studied for block caving projects and mines. Layout design and anticipation of secondary reduction necessities are key factors to which the fragmentation assessment is linked. In addition to the challenge of correctly characterising the input geotechnical parameters for the fragmentation assessment, the fractions of interest are located at the extremes (tails) of the size distribution, where the coarser and finer block sizes occur. At the ‘tails’ of the size distribution, data is scarcer, and statistics are more affected by random variations. Thus, the average and central tendencies of the distribution are of not much practical use. From the tools available for fragmentation assessment, the software Block Caving Fragmentation (BCF) (Esterhuizen 2005) has remained as one of the most used methods to estimate size distribution for block caving projects and mines. In this paper, the new DFN-BCF hybrid approach is described. In this updated method of fragmentation assessment, the primary block generator built into BCF software, has been replaced with a discrete fracture network (DFN) model of the rock mass, making use of the full geometry of the relevant discontinuities that will drive the fragmentation process. Thus, the DFN model is used to obtain in situ and primary fragmentation, while secondary fragmentation is calculated by splitting these blocks applying the BCF algorithm. Several DFN realisations are produced, to cover the range of likely fracture intensities. The final product of the assessment is a weighted fragmentation curve, representing the whole rock mass to be caved, and its corresponding range of variation. It must be acknowledged that volumetric size distribution curves are not intuitive. To aid with the understanding of the results, a novel graphical output has been added to the assessment, consisting of a scaled graphical representation of the actual size distribution at the drawpoints using 3D spheres as a proxy of rock blocks volumes. In addition to the DFN-BCF method description and application, the issues related to the sampling of size distributions at drawpoints are briefly discussed. To date, the DFN-BCF hybrid approach has been calibrated and applied to two world-class block caving projects.

Keywords: block caving, fragmentation, discrete fracture network

Brzovic, A, Hurtado, JP & Marin, N 2014, ‘Intensity rock mass pre-conditioning and fragmentation performance at the El Teniente Mine, Chile’, in R Castro (ed), Proceedings of the 3rd International Symposium on Block and Sublevel Caving, Universidad de Chile, Santiago.
Brzovic, A, Rogers, S, Webb, G, Hurtado, JP, Marin, N, Schachter, P, Alvarez, J & Barahona, K 2015, ‘Discrete fracture network modelling to quantify rock mass pre-conditioning at the El Teniente Mine, Chile’, Mining Technology, vol. 124, no. 3,
pp. 163–177,
Chilès, P, Wackernagel, H, Beucher, H, Lantuéjoul, E & Elion, P 2008, ‘Estimating fracture density from a linear or areal survey’, Proceedings of the VIII International Geostatistics Congress, Universidad de Chile, Santiago, pp. 535–544
Donzé, FV, Bouchez, J & Magnier, SA 1997, ‘Modelling fractures in rock blasting’, International Journal Rock Mechanics and Mining Sciences, vol. 34, no. 8, pp. 1153–1163.
Esterhuizen, GS 2005, A Program to Predict Block Cave Fragmentation - Technical Reference and User's Guide.
Elmo, D, Rogers, S, Stead, D & Eberhardt, E 2014, ‘Discrete fracture network approach to characterise rock mass fragmentation and implications for geomechanical upscaling’, Mining Technology, vol. 123, no. 3, pp. 149–161,
Golder Associates 2021, FracMan Software v 8.0, FracMan Technology Group
Jakubec, J 2014, ‘Fragmentation estimates using BCF software – experiences and pitfalls’, in R Castro (ed), Proceedings of the 3rd International Symposium on Block and Sublevel Caving, Universidad de Chile, Santiago.
Laubscher, D, Guest, A & Jakubec, J 2017, Guidelines on Caving Mining Methods - The Underlying Concepts, WH Bryan Mining and Geology Research Centre, St Lucia.
Laubscher, DH & Jakubec, J 2001, ‘The MRMR rock mass classification for jointed rock masses’, in WA Hustrulid & RL Bullock (eds), Underground Mining Methods: Engineering Fundamentals and International Case Studies, Society for Mining, Metallurgy & Exploration, Englewood, pp. 475–481.
Laubscher, D 1994, ‘Cave mining – the state of the art’, Journal of South African Institute of Mining and Metallurgy, vol. 94, no. 10, pp. 279–293.
La Pointe, P, Wallmann, P & Dershowitz, W 1993, ‘Stochastic estimation of fracture size through simulated sampling’, International Journal of Rock Mechanics and Mining Sciences, vol. 30, no. 7.
Rogers, S, Elmo, D, Webb, G & Catalan, A 2015, ‘Volumetric fracture intensity measurement for improved rock mass characterisation and fragmentation assessment in block caving operations’, Rock Mechanics and Rock Engineering, vol. 48, pp. 633–649.
Van As, A 2021, ‘A generic methodology for cave fragmentation prediction’, course notes, Geomechanics of Cave Mining Hybrid Seminar, Australian Center for Geomechanics, Perth.
Wang, X 2006, Stereological Interpretation of Rock Fracture Traces on Borehole Walls and Other Cylindrical Surfaces, PhD thesis, Virginia Polytechnic Institute and State University, Blacksburg.
Young, D, Boontun, A & Stone, C 1995, ‘Sensitivity tests on rock block size distribution’, in Daemen & Schultz (eds), Proceedings of The 35th U.S. Symposium on Rock Mechanics (USRMS).
Zhang, L, Einstein, HH & Dershowitz, WS 2002, ‘Stereological relationship between trace length and size distribution of elliptical discontinuities’, Géotechnique, vol. 52, no. 6, pp. 419–433.

© Copyright 2024, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
View copyright/legal information
Please direct any queries or error reports to