The Effect of cutoff curtain location on phreatic seepage line and seepage discharge by numerical finite volumes method

The Effect of cutoff curtain on phreatic seepage line position and seepage discharge in earth dams has a great importance. Therefore, in this research, a mathematical model was developed in which general equation of fluid flow in non-uniform, anisotropic soil was discretized by finite volume method, and the position of phreatic line is determined with iteration and deformed mesh method. Calculated and measured position of phreatic line and seepage discharge for different condition of upstream water head shows high accuracy of model. Effect of different position and length of cutoff curtain on seepage discharge and phreatic line position were investigated after model verification. The results showed maximum seepage discharge exists when cutoff curtain is constructed under center of dam bottom. By moving the cutoff curtain location from center of bottom toward toe and heel of dam seepage discharge can be reduces even to 20%. When cutoff curtain location moves from heel toward toe, phreatic seepage line moves to higher situation. Saturated mass volume of dam will increase to 49% when cutoff curtain location moves from middle of dam bottom toward toe of dam. On the other hand, if cutoff curtain constructed in the heel of dam, saturated mass volume decrease only 17.9%. Comparison to no cutoff condition, by increasing cutoff curtain length from 0 to 90% of permeable layer thickness seepage discharge reduces up to 22.8%, but if length of cutoff curtain is equal to total thickness of permeable layer seepage discharge will reduce more than 99 percent.