Don’t Screw This Up! Key pitfalls and important considerations in open pit slope design

Ian de Bruyn

It’s simple right?  You find a resource and you make a hole in the ground to get it out.  How hard can it be?  Open pits are pretty much all the same, and we’ve done this a hundred times before. Chances are “she’ll be right”.  And it is! Until suddenly it’s not alright, very much not alright. When time is short and budget is tight, geotechnics can become the poor relation.  It’s sometimes considered a necessary evil, more likely to cost you money than present you with upside.  And yet that’s not true.  Perhaps one can, after all, go steeper than the 45° that’s routinely plonked into pit shell designs.  Perhaps the money saved on the feasibility study will look a little silly when that unexpected slope failure obliterates the pit ramp. And then there’s safety – perhaps it’s a cliché but its Geotech’s trump card.

Doing the slope design well matters. And doing it well means really understanding slope mechanics and design practicalities, and confidently identifying risks.  So how does it work? OK, you’ve called my bluff.  It’s complicated and we have to make judgement calls.  Confidence wise, it should be better than your horoscope but it isn’t rocket engineering.  It’s also no black box; we can’t just throw in the data, turn the handle and get the results.  And the results, when they do come, have to be handled with care.  So let me see if I can explain this without a 10-part Netflix series. What are the important considerations and key pitfalls in open pit slope design?

About the speaker

Ian de Bruyn Principal Consultant (Geotechnical Engineering), SRK Consulting (Australasia) Pty Ltd

Ian has 26 years’ experience over a wide range of geotechnical engineering projects from feasibility studies through operational support and due diligence studies. Ian originally hails from Durban in South Africa, and left his beloved homeland 20 years ago on a whim for the huge spaces of Western Australia. He hasn’t yet managed to escape its gravitational field.

Ian’s main expertise is in geotechnical investigation and design of slopes for open pit mining operations. He has worked on projects involving very large pits in challenging rock mass conditions in the jungles of New Guinea, the savannahs of Africa, the deserts of Australia and the mountains of South America.

Ian is currently a Principal and team leader of the SRK geotechnical group in Australia.

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