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Evaluation of permeability and hydro-geomechanical behavior of rock masses are one of the most important parameters to the geotechnical studies of the dam sites. Thus parameter is necessary to determine the technical specifications of grouting. Water pressure test (Lugeon) is a common method to evaluation of permeability and hydro-geomechanical behavior of rock masses. This test is carried out in various sections of exploration boreholes at different pressure steps. Behavior of rock masses in the applied pressure and flow, evaluated based on the P-Q diagrams in every section. In this study, the results of Lugeon tests interpreted in 16 exploration boreholes and 120 sections. The behavior of rock masses of dam sites in the respect to permeability and hydro-geomechanical behavior, studied based results of thes