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Slope stability analysis of tailing dam embankments

Knight, Zoe (2015). Slope stability analysis of tailing dam embankments. Bachelor of Engineering (4th Year Project) Thesis, Charles Darwin University.

Document type: Thesis
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Author Knight, Zoe
Title Slope stability analysis of tailing dam embankments
Institution Charles Darwin University
Publication Date 2015
Thesis Type Bachelor of Engineering (4th Year Project)
Abstract The stability of an embankment is a vital consideration in tailings dam design, construction and management. A general overview of dam construction methods, potential failure mechanisms for tailings dam embankments, and different methods of analysis including deterministic and probabilistic analyses are included in this thesis.

Deterministic analysis includes a discussion of the stability of tailings dam embankments by analysing the factors of safety using unique values of each soil, and geometric, property. The factor of safety is calculated using stability charts (Taylor (1948), Bishop and Morgenstern (1960), and Spencer (1967)), and limit equilibrium methods such as those by Fellenius (1936), Janbu (1954), Bishop (1955), Morgenstern and Price (1965), and Spencer (1967). A parametric study and sensitivity analysis were performed to elucidate the effects of varying the shear strength parameters and embankment geometry on the stability of an embankment. Probabilistic methods of analysis use random variables in place of deterministic values to find a range of factors of safety that describes the inherent variability in both the soil and geometry in the tailings dam. A first order, second moment, (FOSM) analysis and Monte Carlo simulations were performed to describe the factors of safety in a risk analysis-based context.

The deterministic and probabilistic methods were applied to simple baseline cases and a case study of an existing tailings dam using hand calculations performed in Microsoft Excel™, and GeoSlope SLOPE/W 2012 software. The embankments were analysed under both short- and long-term conditions (i.e. in terms of both total and effective stress parameters), with the effects of pore water pressure and horizontal seepage considered.

This research found that there were advantages and disadvantages to both the deterministic and probabilistic methods of analysis. The deterministic methods were generally easy to use but the input variables were single values which may not accurately reflect the anisotropy or inhomogeneity within the soil in the tailings dam embankment. This could produce factors of safety that are not representative of the entire embankment. On the other hand, probabilistic analyses took into account such anisotropy and inhomogeneity, but required a more detailed understanding and analysis thereof. It was found that deterministic methods of analysis were suitable in calculating factors of safety, however it is also beneficial to perform probabilistic analyses to find the factor of safety and refined safety margins when the variability from uncertainties is included.
Keyword slope stability
tailings dams
limit equilibrium methods
reliability analysis
Monte Carlo simulation
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Created: Mon, 17 Aug 2015, 09:28:58 CST by Jessie Ng