Seite - 741 - in Book of Full Papers - Symposium Hydro Engineering

affects the safety in relation to different dam heights is calculated and presented graphically in the following figures. Results for sliding Results for overturning Fig. 1. Reduced water level (x-axis) vs. FoS for different dam heights (y-axis). As shown in the above graphs, higher dams are, of course, less sensitive to changes in water levels than lower dams. This is summarized in the following table. Table 3. Effects of changes in water level on the FoS for different dam heights. Change in water level FoS - Sliding FoS - Overturning Dam height 8 m Dam height 30 m Dam height 8 m Dam height 30 m 0,2 m 1,07 1,02 1,05 1,01 1,0 m 1,41 1,09 1,26 1,06 The table shows that changes in water levels have more influence on the FoS against sliding than FoS against overturning. Dam height (i.e. static water pressure) is crucial for how uncertainties in flood calculation and flooding affect stability. When the dam height increases, changes in flood water have little significance for the dam stability. As uncertainties in floods and operating levels will have different impact on the FoS dependent on the dam height, it is reasonable that these uncertainties are handled in the flood calculations and are not included in the FoS. For instance, a dam dependent on floodgates will have other uncertainties related to flood handling and flood levels than a dam with a free overflow spillway. This implies that the corresponding safety factor from static water pressure, should be 1,0. SELF-WEIGHT The self-weight is essential for the stability of a concrete gravity dam. The calculations carried out show that variations in the self-weight is directly related to the FoS and the dam height does not influence the results. 741