ABSTRACT : This work consists of determining rock, mass quality and selecting the appropriate support system of the rock units along the proposed Alaköprü - Ilısu tunnel. The main rock units on the tunnel alignment are marl and limestones. The limestone units are blocky in ophiolitic-melange. The, quality of rock massed on the proposed tunnel and. its suitable support were determined by using RSR (Rock. S tructure Rating) classification. RSR values, were obtained, differently for marl, limestone and matrix of the: ophiolitic-malenge along the power tunnel alignment. Hence, the necessary support systems were suggested, for the power tunnel. The RSR Concept, is useful method for selecting steel rib support for rock tunnel