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Michael Ashley, John Phillips
New guidance and publications relating to tailings dams have been released recently by many jurisdictions across the world as an initial response to recent, well-documented, catastrophic tailings dam failures. The application of new guidelines retrospectively to existing tailings projects can introduce complex challenges, especially for sites with a long and often not well documented history. Challenges can be difficult to overcome while balancing time, cost and risk objectives.
This paper explores the impacts of changes between the 2012 and 2019 revisions of the ANCOLD Guidelines on Tailings Dams and potential implications for existing facilities.
The most significant update between the 2012 and 2019 revisions of the guidelines relating to design practices is the additional detail and guidance on seismic stability analyses and static liquefaction. Guidance on the application of new guidelines for tailings dam designers, owners and regulators is required to provide a consistent approach to manage the risk.
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2020 Papers
2020 – Challenges in applying new guidelines to existing tailings dams projects
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Michael Ashley, John Phillips
New guidance and publications relating to tailings dams have been released recently by many jurisdictions across the world as an initial response to recent, well-documented, catastrophic tailings dam failures. The application of new guidelines retrospectively to existing tailings projects can introduce complex challenges, especially for sites with a long and often not well documented history. Challenges can be difficult to overcome while balancing time, cost and risk objectives.
This paper explores the impacts of changes between the 2012 and 2019 revisions of the ANCOLD Guidelines on Tailings Dams and potential implications for existing facilities.
The most significant update between the 2012 and 2019 revisions of the guidelines relating to design practices is the additional detail and guidance on seismic stability analyses and static liquefaction. Guidance on the application of new guidelines for tailings dam designers, owners and regulators is required to provide a consistent approach to manage the risk.
Learn more
-
$15.00
2020 Papers
2020 – Dynamic Analyses for Static Liquefaction Factor of Safety and Triggering Threshold Values in Tailings Storage Facilities Constructed by Upstream Method
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Qian Gu, Joshua Chan
Tailings Storage Facilities (TSF) constructed using upstream methods may have static liquefaction risks due to the strain softening behaviour of contractive tailings. Conventional Limit Equilibrium Analyses (LEA) using either peak strength or residual strength fail to address the stress-strain compatibilities between materials at different stages of softening or hardening, resulting in over or underestimating embankment stabilities. Static numerical analyses (Finite Element or Difference) are unable to identify the threshold stability due to their inability to converge close to or beyond equilibrium conditions.
In this study the failure triggering process is modelled with dynamic Finite Element Analyses (FEA) with the stress-softening behaviour of contractive tailings simulated by Norsand Model. The embankment failures are identified by either non-zero residual velocities along downstream face, or a drop in average shear stress along potential failure surfaces under increasing disturbing surface pressure. Threshold disturbing surface pressure estimated using these two methods are in close agreements. Factor of Safety (FoS) values estimated from peak mobilised shear strength are found to be between those estimated using the peak and residual shear strength in LEA. q-p’ stress paths in tailings clearly show the stress ratio increasing towards and beyond instability ratio during undrained triggering process. The developments of zones of shear softening and p’ reduction with increasing undrained disturbances help visualise the failure triggering process.
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