Musolino, M, Karakus, M, Cox, D & Nguyen, G 2024, 'Experimental characterisation of fine material for inrush assessment', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 879-893.
(https://papers.acg.uwa.edu.au/p/2435_G-01/)
Abstract: The gravity-fed nature of cave mining allows for uncontrolled flow into mine workings. Given the myriad of triggering mechanisms and complex mix of particles (in terms of shape, size, and mineralogy), inrush events can manifest in several ways with varying levels of risk, making prediction difficult. The primary data input for management decisions are draw point inspections. This study presents several scale model particle characterisation tests demonstrating the uncertainties and difficulties risking inflow potential from draw point inspections. Flow testing reveals that fine clay will have the same flow diameter at ≈ 20% lower moisture content in salt water. The (1:30) scale draw point experiment illustrates how reductions in particle size increase the risk of engulfment to vehicles or personnel. Furthermore, the scale model experiment demonstrates that estimating the fines ratio and moisture content can be complex due to fines percolation and water drainage impediments. A technique was developed to measure (PSD = particle size distribution) in eight zones of the scale model draw point. Results show the percolation of fine material to lower zones, potentially resulting in an underestimate of fine particle ratios by the observer. This work provides foundational knowledge that can inform tactical monitoring solutions such as fixed camera rill angle monitoring, that bridges the gap between long term risk trends (material fining or higher water content) and daily muck pile evaluation. Tactical controls should be an addition to cave scale water monitoring, engineered solutions and production discipline as keys to responsible management of inrush risk.