Hydroelectric power projects are pollution free and renewable sources of energy. These projects involve construction of dams and barrages across the mountainous rivers. In traditional engineering practices, shear strength parameters i.e. cohesion and angle of friction for rock over rock (R/R) and concrete over rock (C/R) interfaces are required for stability analysis and design of dams, slopes and underground structures in or on rock mass. In-situ shear strength parameters may be determined by conducting tests either inside the exploratory drifts or in open trench. In the present study, in-situ shear tests were conducted in open trench at Indira Sagar Polavaram Multipurpose Project Andhra Pradesh. In the present paper, shear strength parameters for R/R and C/R interfaces were evaluated by results of 5 insitu shear tests on C/R interface and 5 tests on R/R interface in the open trench excavated along the spillway axis at Indira Sagar Polavaram Multipurpose Project site. The determination of shear strength parameters involves the measurement of cohesion and friction angle at the failure plane using the Mohr Coulomb’s failure criterion.