Franco Oboni & Cesar Oboni


5. Evaluation Workflow The methodology’s compact algorithm is a quantitative semi-empirical approach. The various hazards, elements constituting the homogeneous dam system to be evaluated are combined following the logic described in Table 2, organized in such a way to reduce redundant calculations and to avoid double counting. This leads to results that have been shown to match, to date, the world-wide portfolio behaviour. Human factors and governance issues are of course built-in together with other paramount details.


Figure 3. Systemic probability evaluation workflow As we will see later, this workflow makes it possible to establish pre-set values of families of underlying


hazards to deliver a priori orders of magnitude of dams probabilities of failure, guide new users as shown in the example of “The Good, Bad and Ugly” dam below. Also, as discussed later it is possible to prepare “scripts” guiding the formulation of what-if scenarios for mitigations such as for instance buttresses, as shown in the last section of this paper.


6. Comparative Analysis of Three Similar Dams


6.1. Dams description: the good, bad and ugly In this section we focus on the comparative analysis of three active, centerline dams, bearing a main tailings distribution line, designed with the same FoS stability criteria:


• FoS drained (ESA): 1.4-1.6 • FoS undrained (USA): 1.3-1.4 • FoS pseudostatic: 1.2 for return =10,000 and 1.3 for return = 2,475


The three dams are under the same climatic conditions, with no water course at the toe. They have berms on the downstream face to control face erosion and are built with selected materials, well-engineered rockfill/earth fill, and a clay core with drainage blanket.


188 | Dam Engineering | Vol XXXIII Issue 3


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