Rock mass geomechanical characterization and evaluation of the support systems of Tepekisla dam and hydroelectric power plant derivation tunnel (Erbaa, Tokat)

In this study, geomecanical characterization of the rock mass and the support systems of the derivation tunnel, which was constructed at a diameter of about 504 m and a diameter of 6.30 m within the scope of Tepekışla Dam and Hydroelectric Power Plant, were evaluated. Within the scope of the preliminary researches in the study, geological survey of the tunnel route, basic geological and geomechanical evaluations and plan of geotechnical site investigation were made. In the scope of design phase studies which were subsequently; detailed geological and geomechanical analyzes, evaluation of geological and geotechnical problems, determination of geomechanical properties of materials and design criteria according to Q, RMR and GSI systems were carried out. Stress and deformation analyzes were performed by using finite element analysis method in the critical sections along the tunnel route to evaluate the validity and performance of the proposed support systems depending on the empirical methods. In the last stage of the construction phase investigations, modifications were made according to the ground conditions of the fortifications as a result of the parameters obtained by geological and geotechnical monitoring, analysis, observation and deformation readings and revised support systems have been proposed and implemented. Numerical analysis results highlighted the importance of numerical analysis results in the occurrence of dent in valley regions which have limit value. The result was that the design phase of the proposed support systems and the construction stages of the support systems were 62% coherent and also 38% inconsistent due to data inadequacy. This 38% inconsistency caused cost increase and waste of time in the construction phase. It was understood that It was important to determine the support system with more data during the design phase, for the field of study in question.