Authors: Lett, J; Castro, R; Pereira, M; Osorio, A; Alvarez, P

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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: Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 561-572,

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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

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