Tailings dams knowledge base creation
Oct 21st, 2020
Tailings dams knowledge base creation is about how to acquire the information needed to perform well documented risk assessments.
Of course, there are many possible ways to create the necessary knowledge-base for a risk assessment that is compliant with the new Global standard. Today we will discuss a few possible ways to do so at a high-level.At Riskope we passionately believe that only a blending of these approaches is capable of bringing the answers needed for high quality risk assessments (e.g. benchmarking, causality analyses, etc.). Of course, the proportion of blending and the intensity of the efforts must be scaled as a function of the project size and resources available.
Historic space observation
Space observation offers numerous possibilities to re-create the history of a facility. These are based on radar interferometry and stereophotogrammetry. Note that we are taking a shortcut here, because both techniques can be deployed from manned or unmanned aircrafts. Furthermore, it is possible that on specific sites good quality stereo pairs going back many years may be available. However, starting in the second half of the seventies, US spy-satellites started bringing back to Earth stereo imagery of various parts of the globe.
The US has now reportedly declassified those images allowing civilians to build, step by step, the history of a tailings facility. We listened to a presentation on this subject by Edumine/Photosat where they showed a real-life example. Let’s note that the precision is claimed to be 15cm. While that is acceptable to gain a general understanding of what happened on a site, e.g.:
- beach lengths,
- overall slope angle,
- dam construction phases and finally
- deposition history,
it certainly is not enough for evaluating the deformations of a dam.
Radar interferometry, together with a number of other specialized sensors, allows to gain a more in depth understanding of, for example:
- ground temperatures and finally
- vegetation stress.
If data are available, the analyses can also go back in time using existing databases.
At Riskope we believe there is great value in approaching the study of a site from an historic point of view using both optical and radar imagery to build the history of the site. Working in Northern Canada we have shown a client the effects of freezing/thawing cycles on a site where, a priori, they were witnessing anomalous deformations. The fact that these repeated each year over the last six years has been reassuring to those involved.
We recommend you use both methods and please start by looking backward! You will have time to then look forward and keep an eye on your structures.
Each time we start a new risk assessment we go through monitoring records. It is long and tedious, and generally very frustrating. Even the exact location of boreholes and monitoring instruments is sometimes not clear, let alone their elevation. In those conditions it is even difficult to understand if, for example, an inclinometer is indeed anchored in bedrock or not. Thus, we see the benefit in using databases and business intelligence platforms, but we also see the hazards. These hide behind beautiful graphics that may be anchored in “alternative reality”.
And then, of course, instruments break down and may not be replaced as they should. Sometimes their placement follows ease of installation rather than the needs of knowledge-building.
Nowadays, measurements can be broadcasted to a central record which in turn can deliver them to a “control room”. There graphic displays can render the global situation of the monitored parameters, in real time. Internet of Things adds wonderful data and Artificial Intelligence may gobble all of this and tell us… what exactly? Let’s remember that AI builds its knowledge on what it feeds on. Indeed, AI is not good, as far as we know, in forecasting something it has never “seen” and is highly unusual. In that sense it is not better than a human being confronted with a new situation. Please discuss this if you have a different opinion.
Thus, again, at Riskope we believe that be the key to allowing IoT and AI to deliver a better job lies in blending. The blending should include backward space observation with as long as possible monitoring history. Do not start with today’s data and hope the machine can help you!
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We have left for last the heavy, annoying and less glamorous, yet paramount part of tailings dams knowledge base creation.
That is to ingest, check and understand the mass of reports that may exist to document a tailings dam. When clients tell us to go visit a tailings operation in order to start a risk assessment, we always try to dissuade them to start that way.
We want to know the dam system before we visit it. As a result, when we go we want to be able to reconnect what we see with what we have learned. Thus, we start by spending days reading and annotating extant reports. That’s the only way we know to discover deficiencies, to evaluate uncertainties and to come up with the KPIs we need to feed ORE2_Tailings.
The good news is that we have found a way to streamline this process thanks to a strategic cooperation with a specialized software company.
Stay tuned, we will get back on this very soon to close the circle of tailings dams knowledge base creation.
Tagged with: dams, deficiencies, interferometry, knowledge base creation, Risk Assessment, stereophotogrammetry, Tailings Dams
Category: Consequences, Optimum Risk Estimates, ORE2_Tailings, Probabilities, Risk analysis, Risk management, Uncategorized