Evaluation of the influence of rapid drawdown in some Colombian earth dam systems and reservoir zones through numerical modeling

Rapid drawdown occurs when the reservoir level drops at such a rate that the material that makes up the slopes surrounding the reservoir or body of the dam is incapable of adequately dissipating the pore pressure. The numerical study of this phenomenon's influence becomes relevant to determine the effect of the variables and provide recommendations for a possible eventuality or the design of future projects. Using the GeoStudio 2012 software, this phenomenon was evaluated using numerical modeling by the simple and coupled analysis of two dams and three existing reservoir areas in Colombia. These structures were subjected to five emptying rates and four cases of drawdown levels. Parametric curves were obtained that represented the behavior of the safety factor in which a height of 2/3 of the normal level resulted in the most significant condition. Additionally, it was determined that the most critical situation corresponds to the day of or the one immediately following the end of the water drop. The simple analysis was greatly affected by the alteration of the conditions and characteristics of the dam soil. Conversely, the coupled analysis was greatly impacted by the drawdown level above the rate. These results made it possible to obtain the intervals of reduction percentages that the safety factor can suffer depending on the drawdown level.