Dynamics of Embankment Slope Stability under Combination of Operating Water Levels and Drawdown Conditions

This study investigated the potential influence of operating water levels and loading conditions on the slope stability of an embankment dam. Four different operating reservoir levels (normal, reduced, embankment height, and overflow) were considered in the study. Numerical modeling was used to investigate the problem in the case of the Chardara dam within the Syrdarya catchment in Kazakhstan. Based on the drawdown rates and operating conditions, minimum factor of safety values ranging from 0.56 (total failure) to 2.5 were retrieved. Furthermore, a very high correlation was observed between drawdown days, the minimum factor of safety values, the maximum factor of safety values, and pore-water pressures, with correlation coefficients ranging from 0.561 to 0.997 (strong to very strong correlation). On the other hand, the highest negative correlation of 0.997 was observed between the minimum factor of safety values and pore-water pressures. Additionally, based on the results from the analysis of variance, three reservoir operating levels (normal, embankment height, and overflow) resulted in p-values less than 0.05, indicating that the variations in the factor of safety values from the drawdown rates were statistically significant. The findings of this study demonstrated that, not only may the drawdown rate be detrimental to the embankments, but that different operating levels can also affect slope stability in different ways.