1. There are distinct differences between calculated safety factors for "heave", "uplift or blowout", and "piping" (internal erosion).2. Similarly, there are differences in the robustness of the safety factor calculations, as the uplift/blowout computations do not take into account the strength of the confining layer. Analysts are encouraged to carefully consider the assumptions of each calculation.3. For any of the mechanisms of heave, uplift, blowout, or backward erosion piping to fully progress to a complete dam failure requires a number of additional steps and conditions, and thus the dam safety practitioner needs to understand the specific failure mechanism involved. The concept that heave and uplift/blowout may be initiators to backward erosion piping (progression) should also be stressed.4. While heave or blowout typically initiates when the reservoir reaches a critical elevation for the first time, backward erosion piping can occur many years after initial impoundment due to progressive and undetected material transport.
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