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Study of the Failure Mechanisms of Mount Polley Tailings Dam Using Numerical Simulations

Salemi Kouchesfahani, Kasra | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51203 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. Mount Polley Tailings Storage Facility (MP-TSF) failed on its perimeter embankment on August 4, 2014, when its 9th construction stage has just been completed. The failure releasedmillions of m3 of toxic tailings, supernatant water and construction materials todownstream. Up to this point, some research studies have been conducted into the causes of the failure. These studies have considered the stability of the TSF in different stages of its construction as well as in the last stage. The aim of the present study is to investigate the causes of the very failure, using numerical methods by the aid of the finite element based software, PLAXIS 2D. In the present study, the results of the previous studies on the stability of the dam in its final state were evaluated and are verified. The results indicate that the breach of the dam occurred due to the undrained failure of a weak layer,namely Glaciolacustrine (GLU) located beneath the breach area, in the dam’s foundation.In addition, a model for simulating the changes in pore water pressure in dam’s both body and foundation during successive stages of construction and consolidation was developed.Based on this model, the safety factor (SF) of the dam was oscillating during the construction and consolidation periods as each construction stage decreased the SF, and each consolidation did thereverse. Moreover, the results of this model indicate that the amount of excess pore water pressure in the GLU layer was significant at the time failure.Such a positive water pressure played a key role in forming the failure mechanism.Finally, some measures which could have prevented the breach if they had been taken before the failure was proposed. The effectiveness of each of the measures was evaluated. It was observed that among the choices constructing a berm in the downstream of the dam could have been the most efficient solution
  9. Keywords:
  10. Slope Stability ; Finite Element Method ; Stability Analysis ; Strength Reduction Factor ; Consolidation ; Mount Polley Tailing Dam Failure ; Foundation Failure

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