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Evaluation of Effect of Phreatic Line Level on Stability of Uupstream Tailings Dams

Azimi Hassani, Nikoo | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45238 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. Tailings dams are considered as one of the most important geotechnical structures and due to the large amount of contaminated tailings deposited behind the dam, any failure of these structures, apart from loss of lives and properties, can be an environmental disaster. Researches show that most of the failure incidents in the last few decades have happened in tailings dams constructed using upstream method. As a result, it is of great significance to study the stability of upstream tailings dams.
    The place of the phreatic line in the dam body plays a critical role in stability of tailings dams. Soil-atmosphere interaction effects such as precipitation, runoff, interception, infiltration, evaporation on one hand, and unsaturated soil effects such as capillary rise on the other, cause significant changes in the situation of the phreatic line.
    In this thesis, first different mechanisms that affect the phreatic line level in the tailings dams and their corresponding equations are studied and a computer program is developed for calculating the fluctuations of the phreatic line. Then, for evaluating the usefulness of the program in real field problems, stability of “Sarcheshmeh” copper mine tailing dam in Rafsanjan city in Iran has been studied. Plaxis software Ver.8.0 has been used for modeling this tailing dam. Necessary parameters for solving the equations and modeling of this dam have been obtained from the results of different laboratory tests on tailings materials and the information available from synoptic stations of the meteorological organization of Iran in the area. After determining the amount of changes in the phreatic level for a special period of time, stability of the dam has been studied based on calculating the factor of safety in different conditions.
    The results show that with constructing new dikes, the safety factor decreases. Also the results show that if all the parameters affecting the phreatic level cause increases of phreatic level the safety factor would be reduced and the stability of the tailings dam would be threatened. Among different parameters affecting the phreatic level, capillary rise found to be the most significant factor on tailings dam’s stability constructed in arid areas
  9. Keywords:
  10. Tailings Dam ; Stability ; Phreatic Line ; Soil-Atmosphere Interaction ; Capillary Effect

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