ABSTRACT
Upper Gotvand dam is constructed on the Karun River at the south west of Iran. In this paper, 2D and 3D models of the dam together with the foundation and abutments were established and several seepage analyses were carried out. Then the gypsum veins that are scattered throughout the foundation ground were included in the models and the seepage pattern, considering the dissolution law of gypsum, was analyzed. It was disclosed that the discharge fluxes obtained from 2D and 3D analyses are not similar and the discharge flux in 3D model is about 4 times that of the 2D model. Also, the 3D model locates the phreatic surface somewhat higher than the 2D model does. This means that the 2D model estimates lower pore water pressure pattern in comparison with the 3D model. These may be attributed to the fact that with 2D model the lateral components of seepage velocity vectors are ignored. In the current case, the rate of increase of discharge flux due to dissolution of gypsum veins was obtained to be a 3rd order function of the aperture width. In spite of the fact that the grout curtain is designed to be some 170 meters deep, however, complete dissolution of gypsum will severely increase the discharge flux through the foundation ground.
