Introduction

Stability analysis during rapid drawdown is an important consideration in the design of embankment dams. The stabilizing effect of the water on the upstream face is lost during rapid drawdown, but the pore-water pressures within the embankment may remain high. As a result, the stability of the upstream face of the dam can be greatly reduced. The dissipation of porewater pressure in the embankment is largely influenced by the permeability and storage characteristics of the embankment materials. Highly permeable materials drain quickly during rapid drawdown, but low permeability materials take a long time to drain. Stability during rapid drawdown can be analyzed using two approaches; namely the “effective strength” approach and the “staged undrained strength” approach. The purpose of this illustrative example is to show how to conduct a rapid drawdown analysis using the stage undrained strength approach.