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Strip and Line versus Blind Sink Shaft Sinking – The Ernest Henry Decision


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Author C J Carr and A E A Northcote


The Ernest Henry Mine (EHM) is owned and operated by Xstrata Copper and is located in North-West Queensland, Australia. The mine is currently undergoing a transition from an 11 Mtpa open pit mine to a large sublevel cave underground mine producing 6 Mtpa. Due to a number of factors, including geometry of the pit and crusher depth, the decision has been taken to develop a hoisting shaft rather than inclined conveyors.

During the feasibility study the strip and line shaft sinking methodology was preferred over blind sinking due to scheduling opportunities and interactions with level development. Other methods of sinking considered included large-diameter raise boring, which was rejected due to concerns relating to centreline accuracy. The strip and line decision was reviewed during the tender process where better than anticipated blind sink advance rates and costs were presented. This in turn enabled the higher cost of the blind sinking method to be justified by a combination of reduced risks including schedule and ground water management.

This paper discusses the pros and cons of both strip and
line and blind sinking methodologies in the Ernest Henry context including
sinking rates and total schedule impacts of the two methods, the key risks
associated with each method, cost implications of blind sinking and safety
implications of the work methods in general. The paper then concludes with the
reasoning behind the decision to change to blind sinking for the EHM shaft.

Carr, C J and
Northcote, A E A, 2011. Strip
and line versus blind sink shaft sinking – the Ernest Henry decision, in Proceedings
11th AusIMM Underground Operators’
19-28 (The Australasian Institute of Mining and Metallurgy: