The selection of the support system is among the most important steps in the design and excavation operation of tunneling projects. The accuracy of this choice is of great importance and has a direct relationship with the executive success of a tunneling project. There are many factors involved in choosing a support system. If all the factors involved in selecting the support system be carefully considered, it will result in a more precise and accurate outcome than the circumstances where only one/more factors are considered. For this purpose, the multiple-attribute decision-making (MADM) method is applied as it provides such a possibility. The preference ranking organization method for enrichment of evaluations (PROMETHEE), multiple-criteria decision analysis method, was used to select the proper support system of the Beheshtabad water transfer tunnel. In this study, based on 6 indices of expense, safety factor, support system efficiency, installation time, movement and mechanization capability through the support system, different scenarios were investigated according to tunnel experts suggestions based on geomechanical-geotechnical and construction conditions of the tunnel. Eventually according to the calculated ranks of alternatives, a support system with an injectable rock-bolt with a 3 m length, 1.5×1.5 m intervals and 10 cm of shotcrete were selected as the most suitable support system for the Beheshtabad tunnel.
