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Numerical Modeling of Stability and Transport of Soluble Contaminants in Tailings Dams under Coupled Hydro-Chemical Processes (A Case Study of Sarcheshmeh Tailings Dam)

Anbarestani, Mona | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56066 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Sadeghi, Hamed
  7. Abstract:
  8. The instability and contamination leakage through tailings dams is one of the major problems of them. These dams are usually constructed through self-consolidation with minimum compaction effort, so special attention must be given to the stability of these structures. In addition, tailings dams contain considerable amounts of metals and chemically soluble contaminants resulting from mining processes in their reservoirs, making them more likely to leak contamination from the dam's foundation and body, causing pollution downstream. The infiltration of various chemical contaminants into the soil may alter its hydraulic and resistance properties. Laboratory studies have shown that pore solution concentrations, including dissolved salt, have an effect on soil characteristics such as hydraulic conductivity, soil-water retention curves, and shear strength. Hydraulic conductivity and water-soil retention curve are the most important characteristics of saturated-unsaturated soils, which are important for the design and analysis of flow, stability, and contaminant transport of geotechnical structures such as tailings dams. Analytical models of soil-water retention curves and saturated hydraulic conductivities have been developed recently, considering saline solution concentration. This study investigates the stability and contaminant transport in the Sarcheshme tailings dam under coupled hydro-chemical flow phenomena using numerical modeling with the simplified assumption of replacing pore solution chemistry with sodium chloride salt solution. The results of this study show that salinity models increased the pore pressure in the transient state compared to the classic pure water model. Furthermore, salinity models and considering salt's effect on shear strength parameters increased the factor of safety and improved the dam's stability both at steady state and during transient conditions. Moreover, salinity models have a greater hydraulic conductivity, so contaminant penetration rates in the dam's body and foundation are higher than in pure water models, which increases advection and diffusion fluxes. Additionally, the flow speed is intensified by the transient conditions of rainfall, precipitation, and evaporation and causes the advection and diffusion flux to increase, which causes more contaminants to penetrate the dam's foundation and body
  9. Keywords:
  10. Tailings Dam ; Structural Stability ; Contaminants Transport ; Soil-Water Retention Curve ; Coupled Flow ; Diffusion ; Unsaturated Hydraulic Conductivity Function

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