# Influence of boundary conditions in DEM models of sublevel caving on dilution and recovery

### Abstract

Discrete element modelling is common approach for analysis of dynamical processes that include granular materials. Method is commonly applied for the modeling of the gravity flow of the broken rock in caving operations. Herein, comparison of two different approaches in such modelling was presented. Two models, ring wide and symmetrically divided, were used for comparison. Ore dilution and recovery were monitored as main comparison parameters, but also the processing time of such models and spatial shape of extraction zones. Ring wide model show greater ore dilution and lower recovery, while half wide models show the opposite results. Cumulative dilution differs for 10%, while ore recoveries differ in approximately 15% for same extraction levels. Also, dilution entrance points are different, where ring wide model shows earlier dilution entrance at about 15% of extraction, while dilution enters at 25% in half wide models. Processing speed is increased in half wide model due to the reduction in number of elements, but overall processing time is nearly the same due to the frequent hang ups inside the half wide model. Shape and size of the extraction zones are very different. Half wide model shows much higher extraction zone in contrary with ring wide, while depth of extraction zone is greater in ring wide models which corresponds with higher and earlier entry of dilution.

### References

BONILLA-SIERRA et al. (2015) Rock slope stability analysis using photogrammetric data and DFN--DEM modelling. Acta Geotechnica, Volume 10, pp. 497-511.

BRIDGWATER, J., COOKE, M. H. and SCOTT, A. M. (1978) Interparticle percolation: equipment development and mean percolation velocities. Trans. I Chem. E, Volume 56, pp. 157.

CASTRO, R. L., GONZALEZ, F. and ARANCIBIA, E. (2009) Development of a gravity flow numerical model for the evaluation of drawpoint spacing for block/panel caving. Journal of the Southern African Institute of Mining and Metallurgy, Volume 109, pp. 393-400.

CHEN, G. (1997) Stochastic modeling of rock fragment flow under gravity. International Journal of Rock Mechanics and Mining Sciences, Volume 34, pp. 323-331.

CUNDALL, P. A. (1971) A computer model for simulating progressive, large scale movement in blocky rock systems. In: Proceedings of the International Symposium on Rock Mechanics, pp. 129-136.

DEGAGNE, D. et al. (2006) The influence of cave mass properties on discrete sublevel cave models. In: Golden Rocks 2006, The 41st US Symposium on Rock Mechanics (USRMS). American Rock Mechanics Association..

DEGAGNE, D. O et al. (2005) The Influence of Blasting Fragmentation on Ore Recovery in Sublevel Cave Mines. In: Alaska Rocks 2005, The 40th US Symposium on Rock Mechanics (USRMS). American Rock Mechanics Association.

GUSTAFSSON, P. (1998) Waste rock content variations during gravity flow in sublevel caving: Analysis of full-scale experiments and numerical simulations. Thesis (PhD), Luleå University of Technology.

HENDERSON, A. et al (2004) The ParaView Guide. Kitware Clifton Park, NY.

ITASCA, P. (2008) Particle Flow Code in 3 Dimensions, User's Guide.

KACMAR, L. (2008) Theoretical aspects of new options of sublevel caving methods. Acta Montanistica Slovaca, Volume 13, pp. 448-453.

KLOSS, C. et al. (2012) Models, algorithms and validation for opensource DEM and CFD--DEM. Progress in Computational Fluid Dynamics, an International Journal, Volume 12, pp. 140-152.

KVAPIL, R. (1965) Gravity flow of granular materials in Hoppers and bins in mines—II. Coarse material. In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. Pergamon, pp. 277-292.

KVAPIL, R. (1982) The mechanics and design of sublevel caving systems. Underground mining methods handbook, pp. 880-897.

LAPČEVIĆ, V. and TORBICA, S. (2017) Numerical investigation of caved rock mass friction and fragmentation change influence on gravity flow formation in sublevel caving. Minerals, Volume 7, pp. 56.

MILIĆ, V., et al (2014) Research results on application of semi-level induced caving with lateral loading in ore body Borska Reka. Podzemni radovi, Volume 22, pp. 1-9.

MUNJIZA, A. A. (2004) The combined finite-discrete element method. John Wiley & Sons.

NEDDERMAN, R. M. (2005) Statics and kinematics of granular materials. Cambridge University Press.

RUSTAN, A. (2000) Gravity flow of broken rock: What is known and unknown. In: International Conference & Exhibition on Mass MiningThe Australasian Institute of Mining and Metallurgy.

SCHOLTÈS, L. U. C. and DONZÉ, F.-V. (2012) Modelling progressive failure in fractured rock masses using a 3D discrete element method. International Journal of Rock Mechanics and Mining Sciences, Volume 52, pp. 18-30.

SELLDÉN, H. and PIERCE, M. (2004) PFC3D modelling of flow behaviour in sublevel caving. In: MassMin 2004—Proceedings, pp. 22-25.

SHI, G.-H. (1992) Discontinuous deformation analysis: a new numerical model for the statics and dynamics of deformable block structures. Engineering computations, Volume 9, pp. 157-168.

ŠMILAUER, V. et al. (2015) DEM formulation. In: Yade Documentation 2nd ed.

STAZHEVSKII, S. B. (1996) Features of flow of broken rock in extraction of ores with sublevel caving. Journal of Mining Science, Volume 32, pp. 403-416.

THOENI, K. et al. (2014) A 3D discrete element modelling approach for rockfall analysis with drapery systems. International Journal of Rock Mechanics and Mining Sciences, Volume 68, pp. 107-119.

TRAN, V. D. H., MEGUID, M. A. and CHOUINARD, L. E. (2012) A discrete element study of the earth pressure distribution on cylindrical shafts. In: Tunnelling Association of Canada (TAC) Conference 2012, Montreal.

TRAN, V. D. H., MEGUID, M. A. and CHOUINARD, L. E. (2014) Three-dimensional analysis of geogrid-reinforced soil using a finite-discrete element framework. International Journal of Geomechanics, Volume 15.

WILLIAMS, J. R. (1985) The theoretical basis of the discrete element method. In: Proc. of the NUMETA'85 Conference.

WILLIAMS, T. et al., (2017) Gnuplot 4.5: An Interactive Plotting Program. 2011. [Online] Available from: http://www.gnuplot.info [Accessed 25/5/2017]

*Podzemni Radovi*, (33), 1-15. Retrieved from http://ume.rgf.bg.ac.rs/index.php/ume/article/view/124

This work is licensed under a Creative Commons Attribution 4.0 International License.