Assessment of stability of slopes under drawdown conditions

The traditional approach for estimating the stability of slopes under different submergence conditions is the charts of Morgernstern and, more recently, proprietary computer programs, both utilizing limit-state analyses. The chart approach is limited by geometry and material property considerations and the limit-state approach by assumptions about analysis method and failure mechanism. The finite-element method offers a powerful method for analyzing complex geometries and properties of slope stability problems, but may be unattractive for routine use by supervisory staff. By comparison a chart based approach is useful, particularly when setting operating conditions on, for example, drawdown rates for dams and reservoirs. This paper seeks to explore the use of the finite-element method to produce operating charts for such circumstances that should be applicable to real structures.