SLM and the Probability of failure of a tailings dam

SLM and the probability of failure of a tailings dam goes back 35 years.  A paper entitled “Probability and Risk of Slope Failure” (Silva et al., 2008) proposed using quantification of expert judgement.  That is a subjective/semi-empirical probability evaluation as a practical alternative for determining probability of slope failure. We call this approach SLM, using the initials of the authors. SLM culminates with semi-empirical relationships between Factor of Safety -FoS- and probability of failure -pf-. That relationship allows to estimate…

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Strategic operational and tactical planning for tailings hydro dams

We are learning that structural integrity of hydro dams is also becoming an issue. Thus, similarly to tailings dams, we need a strategic operational and tactical planning for tailings hydro dams! Karl Terzaghi, American Society of Civil Engineers, “Terzaghi Lectures, 1974-1982,” American Society of Civil Engineers (1986) ISBN 0-87262-532-X. proposed that a dam rating system should provide ALL of the following: A logical framework for rating the relative safety of a dam Allow for the use of judgment and experience…

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Dam risks informational gap

Dam risks informational gap impacts to a certain extent all dams: hydro, tailings and finally, toxic dumps. There are thousands of active dams around the world significantly different because of: age, function, materials, construction style and care, maintenance care and finally “behavior” or performance. Oroville dam was one of those, like other recent mining catastrophes and the Michigan failures. What do all dams have in common? Dams are all exposed to hazards, e.g. natural, man-made such as excess of confidence,…

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Comparison of ORE2_Tailings estimated dam failure probabilities

The comparison of ORE2_Tailings estimated dam failure probabilities is an important element of Riskope continued commitment to test the validity of the approach. Quantitative risk assessment in tailings One can perform a Quantitative Risk Assessments (QRA) using various methods. Indeed, for tailings dam risks, they all consist in evaluating the: probability of failure of the dam generated by various pertinent hazards, potential consequences of a dam system collapse (failure) and finally the risk. The technical and mathematical tools for performing…

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Global Industry Standard on Tailings Management

On Wednesday August 5th ICMM, UNEP and PRI launched the Global Industry Standard on Tailings Management. In this blogpost we offer some comments on the Global Industry Standard on Tailings Management. We salute this initiative that we have supported already at draft level. Indeed, at that time we wrote our comments and notes via email and online portal. That was following the public Consultation invitation which gathered a total of 629 responses. The consultation report We found the Global Tailings…

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Dam Monitoring Effects

Dam monitoring effect is a case history. A client acquired a mining properties portfolio. It included inactive dams at closed mines. Some of these structures were relatively well documented, while others were not. As a result, the client was facing important decisions, one of them being the effort to enhance the knowledge on the structures. The question the client asked was: “What happens to a particular dam if the level of knowledge we have on an inactive dam goes from…

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Tailings dams design and experience

Lately several tailings dam failures rocked the mining world. Despite the relative high frequency of these events we have heard engineers qualify the failures as “one in a million”, “extremely rare” or even “black swans”. Today we want to discuss a few concepts on tailings dams design and experience. In particular, we will focus on some disconcerting qualifiers like the ones we just cited above. For example, given the experience of tailings dams catastrophic failures  resulting from combinations of various…

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Not all risk assessments are created equal

The UNEP “Mine tailings storage: safety is no accident” report asks mining companies to make environmental and human safety a priority. To ensure mining companies meet that result in management actions and ground operations, a residual risk assessment should be performed. For clarity, residual risk assessments are those that intervene after mitigations or critical controls.  However not all risk assessments are created equal so let’s explore the differences. What are the requirements for a good risk assessment? Risk assessments are…

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