Authors: Hooman, M; van den Berg, L; Mohle, H; Paiken, L

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DOI https://doi.org/10.36487/ACG_repo/2205_23

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Hooman, M, van den Berg, L, Mohle, H & Paiken, L 2022, 'Ventilation requirements of cave mines', in Y Potvin (ed.), Caving 2022: Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 343-354, https://doi.org/10.36487/ACG_repo/2205_23

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Abstract:
Cave mining methods have been used at more than 30 operations globally. Projects are currently underway to plan block cave, panel cave, and sublevel cave operations. Cave mining methods are typically considered at near-vertical orebodies where precious and base metals will be produced. These mining methods are viable options as they offer high production rates and relatively low operating costs. Production footprints are generally concentrated with supporting services like material handling systems, workshops and other services close to the production footprint. These mines start with high upfront costs to access the production footprint before generating revenue at relatively lower operating costs. Block cave and panel cave mines are established under the controlled collapse of the rock mass under the force of gravity from the bottom up. The block or panel is de-stressed at the apex and undercut levels. The orebody is allowed to cave on the extraction level, and rock is drawn from drawbells as the rock is broken up as it descends as part of the production process. A sublevel cave mine involves drilling and blasting between mining levels and uses a top-down approach to extract the orebody. Sublevel cave mines can start to generate revenue earlier at lower upfront costs. However, production rates achieved in sublevel caving operations are typically lower than for block cave mines. One of the engineering disciplines requiring a unique approach for block and sublevel cave mining is ventilation. Ventilation designs must ensure production ramp-up is met during the construction phase and that steady-state operations can achieve unconstrained production. Ventilation benchmarking has been developed from the existing mines and provides confidence during the study phase. Benchmarks typically cater for steady-state operations, but the ventilation pinch-point of these cave mines is during the construction phase. Ventilation needs are significantly more during the construction phase than during steady-state operations. The construction phase includes development at the undercut, production, ventilation and ore transport levels and other fixed services that need to be ventilated simultaneously while production is started. Ventilation planning needs to include the construction and steady-state phases considering the mine design criteria to arrive at the required ventilation, potential mechanical refrigeration, and dust management strategies to support employees’ safe and healthy underground conditions. As a result of concentrated mining, ventilation-on-demand and controlled partial recirculation of ventilation districts can be considered. During the construction phase, temporary versus permanent refrigeration can be carefully designed to provide production flexibility while keeping capital expenditure to a minimum. Trucking loops, strategic positioning of air coolers, dedicated return airways and airways eliminating worker exposure to dust loading and diesel heat need to be optimally designed. This paper provides design guidelines to arrive at ventilation requirements over life-of-mine to support unconstrained production and the health and safety of workers underground.

Keywords: ventilation, block cave, sublevel cave, design, requirements

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