Determination of the optimum sealing method for Azad pumped storage dam considering seepage analysis

Abstract

Seepage analysis of the upper reservoir of the Kurdistan Azad pumped storage dam with a volume of 3.8E+5 m3 is a key step for selection of the optimized sealing method. More than 60% of the Lugeon test results show very permeable behavior for the pit and abutments of the reservoir. In this study, regarding the permeability value of the reservoir abutments and pit obtained by means of Lugeon tests, seepage rate was computed using various analytical and numerical methods. Reservoir total seepage discharge was computed in steady-state regime by means of analytical and numerical methods (SEEP/W finite element software) as 1.14E+05 and 1.15E+05 m3/day, respectively. Distinct element method (UDEC software) showed variable behavior for the seepage flow. In the reservoir initial impounding stages, the amount of seepage was very high (1.70E+06 m3/day). Then, the seepage rate decreased gradually and reached to a constant value (1.12E+05 m3/day). For the reservoir 3D modeling, Seep3D commercial software was used and has shown water seepage discharge of about 1.18E+05 m3/day, means 3% of total reservoir volume. Based on the above-mentioned results and regarding behavior of seepage in the initial impounding stages, sealing element is necessary to prevent from seepage phenomenon. Clay blanket, concrete lining, asphaltic concrete, and geosynthetic are the proposed methods in a large water reservoir. After a feasibility study on various sealing methods, geomembrane was suggested as the best sealing method with the reasonable implementation cost.