Water tables placed against earth levees over time will adjust to steady state conditions. If the water level against the earth levee is suddenly lowered then pore-water pressures in the earth levee may not dissipate fast enough and can lead to a slope failure situation. The following example is used to illustrate the use of the total stress method (Duncan three-stage) for rapid drawdown analysis of a two-dimensional storage dam model. The purpose of this model is to document the correct solution of the rapid drawdown methodology as presented by Duncan et al. (1990).
The pumped storage project dam has a densely compacted, silty clay core. The lower portion of the upstream slope is a random zone with the same strength properties as the core. The upper portion of the upstream slope and all of the downstream slope is a free draining rockfill. The rapid drawdown analysis water level is from 545 feet to 380 feet.