Authors: Durkin, SP; Moore, BT

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Durkin, SP & Moore, BT 2020, 'The safest way to increase overall pitwall slope', in PM Dight (ed.), Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 1413-1424,

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The overall pitwall slope angle of an open pit mine is a critical engineering factor in determining stripping ratio in any given mine. The reduction of stripping ratio results in revaluation of every block of mineralised material within a resource. It generally increases the ore reserve thereby increasing resource utilisation and in most cases will result in improved net present value of a given orebody. Slope stability risk analysis will generally determine the critical element of inter-ramp angle with other features around berm crest width and batter angle. The easiest way to impact overall pitwall slope without interfering with the inter-ramp slope is to reduce the width requirement of the ramp. There are many ways to do this. Safescape's patented Edge Protector product is a modular cantilever wall that creates a vertical front face to a rock bund. This results in a reduction of up to half of the road width taken up by rock bunds used as edge delineation for haul roads. This change has a positive impact on the economics and sustainability of most open pits. Various factors including depth, size of trucking fleet, optimised stripping ratio and interramp slope all play a part in determining how much value can be achieved. The Edge Protector system also reduces the likelihood of trucks driving over a rock bund. To penetrate a bund, trucks need to engage the soil force of the material immediately behind the barrier, thus reducing their speed. Mathematical analysis by The University of Western Australia and field testing has provided the authors with a way of providing a level of engineering confidence around truck interactions with rock bunds that was not previously possible.

Keywords: edge protection, risk, hazard, pit slope, safety

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