Influence of Permeability Anisotropy on Seepage and Slope Stability of an Earthen Dam During Rapid and Slow Drawdown

Permeability one of the most significant parameters influencing reservoir performance is the accessibility that fluids flow through, this study investigates the influence of anisotropic permeability on seepage patterns and slope stability of an earthen dam during rapid and slow drawdown conditions using physical and numerical modeling.Physical modeling using a small-scale dam model and numerical simulations using SEEP/W and SLOPE/W were performed for rapid and slow drawdown scenarios.The present study focuses on the impact of hydraulic anisotropy and soil characteristics on the seepage rate and the stability evaluation of the upstream and downstream slopes for rapidly and slow drawdown scenario during transient flow regime and compared the findings with numerical results.The results show that anisotropic permeability increased seepage rates by over 75% and reduced slope stability by over 55% compared to the isotropic case.The effects were more significant for rapid drawdown conditions.Moreover, effects of hydraulic anisotropic on the physical model's progress to saturation and the period of time needed for reaching saturation (steady state) has been twice as long as it takes an isotropic model to finally reach saturation, this is because a drop in saturated hydraulic conductivity levels causes flow rates to decrease, which in turn causes a gradual development of seepage inside the earth dam.The study demonstrates the importance of incorporating anisotropic permeability for accurate prediction of seepage and slope stability during drawdown.