Introduction

Embankment dams are large earth or rock dams that depend on the shear strength of the compacted material to withhold the water pressure of the upstream reservoir. An important consideration for embankment dam design is the dam stability during reservoir drawdown. Under operating conditions, the reservoir water pressure has a stabilizing affect on the upstream dam face. During rapid reservoir drawdown, the stabilizing effect of the water is lost but the pore-water pressures within the embankment may remain high. Consequently, the dam stability along the upstream face may decrease until the high pore water pressures within the embankment dissipate. Pore water pressure dissipation depends on the permeability and storage characteristics of the embankment materials. Highly permeable materials drain quickly during rapid drawdown, while low permeability materials take a long time to drain.

This example demonstrates a simple method for modeling the effects of rapid drawdown on embankment dam stability.