selection of optimum tunnel support system using aggregated ranking of saw, topsis and la methods

the selection of optimum support system is a key step in the successful design operation of tunneling, rock mass stabilization and minimization of plastic zone extension around a tunnel. in this context, it is not sufficient to rely only on the experiences of design engineers, but taking all effective measures and parameters is necessary to do a proper choice. in this paper, multi attribute decision making (madm) methods including simple additive weighting (saw), technique for order preference by similarity to ideal solution (topsis), and linear assignment (la) are used for selection of a proper support system for beheshtabad water transporting tunnel from among the six proposed support systems by considering the attributes of cost, safety factor, applicability, installation time, displacement and capable of mechanization. aggregating the results of ranking by the ranks mean, borda and copland techniques led to the suggestion of a support system of injectional rock-bolt 3 m in length with 1.5×1.5 m distance together with shotcrete by 10 cm in thickness.