A Numerical Modeling Study for Determining the Optimal Depth of Grout Curtain in Foundation and Abutments of Karun 4 Dam

Some experimental relations have been developed for determining the grout curtain depth, but these relations cannot be applied to any dam with any geological condition. Therefore, the effect of the grout curtain depth on seepage through foundation and abutments of each dam should be studied separately. To examine this parameter in Karun 4 dam, the numerical modeling method was applied using FLAC in a 2-dimensional modeling process. Permeability coefficient is an important parameter in numerical modeling. In this research, the experimental relationships for Lugeon values and permeability coefficient were used to determine the required permeability. A transverse section was used to model each of the abutments and the foundation of Karun 4 dam. The grout curtain was designed as a wall with a very low permeability at different depths. After modeling the grout curtain with various lengths, the curtain depth was determined based on seepage level, curtain flow efficiency, drilling-injection costs, and value of seepage water. The grout curtain depths were calculated to be 70, 184, and 104 at the foundation, left abutment, and right abutment, respectively. Also analysis of the pore water pressure and flow lines shows when the curtain is sewed to the Pabdeh Formation, we have the high efficiency in the grout curtain.