Lett, J, Castro, R, Pereira, M, Osorio, A & Alvarez, P 2022, 'BCRisk applications for rill swell hazard analysis in PC1: case study at Cadia East Operations', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving
, Australian Centre for Geomechanics, Perth, pp. 561-572, https://doi.org/10.36487/ACG_repo/2205_38
Several geotechnical hazards can affect productivity and safety at a drawpoint level in caving mines, including rockbursts, inrushes, collapses and air blasts. One such issue observed at Cadia East Panel Cave 1 (PC1) and Panel Cave 2 (PC2) sectors is the rill swell of fines (RS), a phenomenon in which a large volume of dry, fine material suddenly enters the extraction drives from a drawpoint. In order to gain an understanding of this phenomenon, a conceptual model was proposed. Additionally, a detailed exploratory analysis and subsequent logistic regression modelling were conducted to investigate this hazard from field observation at the PC1 sector at Cadia East Operations (CVO). The analysis indicated that the main variables influencing rill swell probability are the height of draw (HOD), the previous rill swell event, the location of the drawpoint relative to the cave back shape, the extraction rate, and draw control variables such as uniformity and Delta HOD. Based on the statistical analysis, a logistic regression model was built, thus classifying the drawpoints under high and low risk at PC1. The fitted model was able to classify the rill swell events in the short-term, obtaining an accuracy of 87%. The mathematical models have been implemented in BCRisk®, a machine-learning and draw control software currently used at the mine. The results of the BCRisk implementation in PC1 and PC2 show that hazard models are a useful tool for geotechnical analysis and mine planning at Cadia East operations. Results from this study have been useful in defining and controlling short-term planning parameters to mitigate the rill swell hazard.
Keywords: inrush, rill swell, mine planning, underground mining, geotechnical hazards
BCTEC 2018, BCRisk, Version 4.0, computer software, Santiago, Chile.
BCTEC 2019, Swell rill of fines. Report 1: Rilling of fines analysis, modelling and operational rules for Cadia Valley Operations, Internal Report.
BCTEC 2022, Rill Swell analysis and modelling in BCRISK® 4.0 for PC1-PC2 Cadia Valley Operations, Internal Report.
Brown, ET 2012, ‘Progress and challenges in some areas of deep mining’, in Y Potvin (ed.), Deep Mining 2012: Proceedings of the Sixth International Seminar on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 1–24.
Fawcett, T 2006, ‘An introduction to ROC analysis’, Pattern Recognition Letters 27(8): pp. 861–874.
Flores-Gonzalez, G 2019, ‘Major hazards associated with cave mining: are they manageable?’, in J Wesseloo (ed.), MGR 2019: Proceedings of the First International Conference on Mining Geomechanical Risk, Australian Centre for Geomechanics, Perth, pp. 31–46.
Geng, P & Sakhanenko, L 2015, ‘Parameter estimation for the logistic regression model under case-control study’, Statistics & Probabilities Letters, 109: pp. 168–177.
Hartman, H & Mutmansky, J 2002, Introductory Mining Engineering, 2nd edition. Wiley, Hoboken.
Hosmer, D, Lemeshow, S & Sturdivant, R 2013, Applied logistic regression, vol 398, Wiley, New York.
King, G & Zeng, L 2001, ‘Logistic regression in rare events data’, Political Analysis, vol 9 (2), pp. 137–163.
Lett, J, Brunton, I, Capes, G, Jager, A, Mobilio, B, Rachocki, J, Sharrock, G & Secheny, M 2016, ‘Undercutting to surface breakthrough – Cadia East panel cave (Stage 1)’, in Proceedings of the Seventh International Conference & Exhibition on Mass Mining (MassMin 2016), pp. 65–81.
McCullagh, P & Nelder, J 1989, Generalized linear models, 2nd edition, Chapman & Hall, London.
Orrego, C, Lowther, R & Newcombe, G 2020, ‘Undercutting method selection at Cadia East PC2–3 extension’, in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining, University of Chile, Santiago, pp. 370–384
Susaeta, A 2004, ‘Theory of Gravity Flow (Part 2)’, In Proceedings MassMin 2004, pp. 173–179.