Survey

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

no text concepts found

Transcript

Figure 3.8: Schematic of embankment after slip circle failure Factors of safety of tailings dam embankments can be calculated from stability charts, limit equilibrium methods, probabilistic analysis methods, finite element analysis methods, or a combination thereof. The first three methods are discussed in this thesis. 3.2.1 ANCOLD recommendations ANCOLD (2012) state that factors of safety depend on the consequences of failure, material properties, and subsurface conditions: there are no ârulesâ governing what constitutes an acceptable factor of safety. Recommended minimum factors of safety for tailings dams under different loading conditions are shown in Table 3.1. Table 3.1: ANCOLD recommended factors of safety for tailings dams (ANCOLD, 2012). Loading condition Recommended minimum factor of safety Shear strength to be used for evaluation Long-term drained 1.5 Effective Short-term undrained (potential loss of containment) 1.5 Consolidated undrained Short-term undrained (no potential loss of containment) 1.3 Consolidated undrained When there is âno potential loss of containmentâ in short-term undrained conditions, a lower factor of safety is recommended. This is not recommended for those cases analysed in this thesis since the factor of safety assumes a âsaferâ embankment with no loss of containment. It cannot be determined that a tailings dam constructed to a factor of safety of 1.3 will never have any loss of containment. Therefore, the minimum factor of safety, in this thesis, has been calculated assuming the worst conditions (i.e. including the potential loss of containment) as this is what better represents a real embankment failure. 24