Rockfall risk — how well do we understand the consequences of the decisions we make?

Authors: Rwodzi, L; Joughin, W; Stacey, TR

DOI https://doi.org/10.36487/ACG_rep/1108_14_Stacey

Cite As:
Rwodzi, L, Joughin, W & Stacey, TR 2011, 'Rockfall risk — how well do we understand the consequences of the decisions we make?', in Y Potvin (ed.), Strategic versus Tactical 2011: Proceedings of the Fourth International Seminar on Strategic versus Tactical Approaches in Mining, Australian Centre for Geomechanics, Perth, pp. 179-194, https://doi.org/10.36487/ACG_rep/1108_14_Stacey

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Abstract:
The consequences of rockfalls in the narrow tabular mining geometry typical of the gold and platinum operations in South Africa are numerous and vary depending on rockfall size and applicable remedial strategy. Rockfalls are a significant cause of mining accidents, and also result in losses to the mining operation due to such accidents as well as reduced productivity, dilution, re-supporting, and loss of sweepings. Pillars and remnants may also have to be left, which results in loss of ore, reducing the available reserves. While these financial losses can be significant, there are commonly no records of the evaluation of such losses on mines. The financial evaluation of risk mitigation is usually tactical, being based only on the cost of implementing a support system, and does not take into account the losses resulting from accidents and incidents. The losses associated with rockfalls for different support designs are rarely quantified, hence the question, “How well do we understand the consequences of the decisions we make?” A more realistic evaluation of alternative support designs should compare the total cost of implementing the support system and the inherent risk of rockfalls. To determine the inherent risk of rockfalls, the consequences of rockfalls must be identified and quantified. In this paper, a generic methodology to quantify the cost of the losses associated with rockfalls is proposed. The methodology was developed after extensive research was conducted on two South African narrow tabular mining operations. The methodology enables the calculation of risk associated with different support options, and the risk is expressed in monetary terms (South African rands are used in the paper), a language well understood by management. Management can therefore be involved in the design of risk mitigating systems, since they can determine the acceptable risk that the rock engineer can apply in the support design. Safety and value to the mining operation can therefore be optimised, which represents a strategic approach to rock support design rather than the tactical approach that is currently practised.

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