Stability analysis of valley-type upstream tailings dams using a 3D model

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Abstract
The upstream valley-type tailings dam exhibits a longitudinal profile that resembles an inverted triangle or a shape approximating an inverted triangle. This unique dam structure and its mechanical characteristics mean that the influence of longitudinal stress on the stability of the dam cannot be overlooked. However, the two-dimensional Swedish slip circle method calculation model does not take into account longitudinal stress, necessitating the development of a three-dimensional model specifically for the stability analysis of upstream valley-type tailings dams. Utilizing the Beijing Lizheng Geotechnical Calculation Software 5.3 standalone version, a three-dimensional calculation model was constructed based on the Swedish slip circle method. Taking the Cangyuan Jinla Lead-Zinc Mine tailings dam as an engineering example, this model was used to calculate five cross-sections, including 1–1′, of the dam. The results were then compared and analyzed with those obtained from the Swedish slip circle method, the simplified Bishop method, and the Janbu method. Using this three-dimensional model, the safety factors for cross-sections 1–1′, 2–2′, 3–3′, 4–4′, and 5–5′ of the tailings dam were calculated to be 2.798, 1.348, 1.332, 1.466, and 2.134, respectively. Analysis concluded that the most dangerous sliding surface of the tailings dam is located at the 3–3′ cross-section, with an overall dam safety factor of 1.332, indicating that the tailings dam is in a relatively stable condition. The safety factor of the tailings dam calculated using the finite element software MIDAS is 1.3531, verifying the accuracy of this three-dimensional model. For upstream valley-type tailings dams, the results from ordinary two-dimensional models tend to be on the dangerous side and thus should be corrected using this three-dimensional model to obtain more accurate and conforming safety factors.

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