Seepage analysis OfTarbela dam (Pakistan) using finite element method

The performance data on seepage control of Tarbela Dam, which was completed in 1975 in Pakistan, is analyzed using Saturated-Unsaturated Seepage Flow Finite Element analysis based on the Invariant Mesh technique. Computer code UNSAF2D has been used for the analysis. The monitoring data is collected to compare with the theoretically calculated values. The analysis is done for the various stages of reservoir filling, depleting and various conditions of sedimentation in the reservoir. The comparison, generally, shows a good agreement between calculated and observed values. One of the pronounced feature of the Tarbela dam is its very wide upstream impervious blanket. The purpose of the construction of this blanket was to control the seepage and the uplift pressure of the dam built on the very thick alluvium deposit of the Indus river. The calculated results explain the function of this upstream blanket, and also its change of permeability characteristics with time due to accumulation of large amount of sediment on it.