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PublisherThe University of Arizona.
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EmbargoRelease after 07/16/2021
AbstractTailings storage facilities (TSFs) are among the largest geotechnical structures in the world and operate for adequate and safe storage of tailings during and after mining activities. Ensuring the stability of these enormous structures has been a long-standing environmental liability for mining-related communities; the failures of TSFs can not only undermines the sustainable development of a mine, but also can cause irreparable hazards and damage to those communities and environments. This document presents research regarding three main topics related to TSFs water management. The first topic is development of site-specific guidelines for safe TSF water management. In this regard, the study focuses on determining the optimal beach distance from the decant pond to the crest, which can be a practical and easy monitoring criterion for securing TSF stability. 2D stress-seepage coupled analyses were conducted to evaluate geotechnical stability; additionally, water increments that increase due to unexpected weather conditions (heavy rainfall and strong wind) were considered for the optimal beach distance. The results of this research can be useful in developing a TSF risk level guideline of the testing site. The second topic is investigation of the potential of an environmentally-friendly polymer as a new drag reduction agent (DRA) to reduce frictional pressure loss and also to conserve water. Lab-scale pipe loop tests examined the effect of the polymer on the pressure loss of the tailings slurry in pipe flows. The experiment results confirmed the potential for using the polymer as a new DRA. Findings showed that pressure loss decreased with increasing polymer percentages up to 4%, but increased above concentrations of 4%. 3D numerical models of computational fluid dynamics (CFD) simulations were developed and validated based on the pipe loop test results. The model provided the potential amount of water and transportation energy saving with minimal changes of pressure loss, induced by solid concentration increases. The final topic deals with usage of the new DRA. When the DRA is employed and solids concentration is increased, the study explored the relevant operating issues, such as settling of tailings particles in pipelines, and accelerating pipeline wear using 3D CFD numerical simulations. The polymer used in the second study reported here was expected to improve the efficiency of tailings slurry flows in pipelines. The results confirmed that by employing the new DRA, the minimal changes of pressure loss levels could be achieved even though there were increases in solids concentration. The polymer also increased the flow velocity, making it possible to transport tailings faster than the critical velocity at which the particle settlement begins. Also, the addition of the polymer resulted in an increase of the erosion rate, due to increased flow velocity, but the total amount of erosion was reduced at certain solids concentrations.
Degree ProgramGraduate College