Selection the appropriate retaining structure for excavations using fuzzy TOPSIS approach (Case study: Ilam city)

Selecting the appropriate retaining structure to stabilize excavation walls is a complex and sensitive decision at each building project. The decision making process of this matter includes many uncertain and inexplicit criteria as well as surrounding adjacent buildings conditions and, of course, engineering judgment. The TOPSIS are widely applied to evaluate alternatives related to multiple decision criteria. Nevertheless, the TOPSIS are incapable of dealing with the inherent subjectivity and ambiguity existing in the mapping of the decision-maker’s judgment for exact numerical values, therefore fuzzy multi-criteria decision-making and fuzzy logic have been combined. In this study, Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is used for Ilam town, Iran, as a case study to make an appropriate selection. This selection includes 3 alternatives and 7 criteria adopted for various ground types and different excavation depths. After considreing the appropriate alternatives and determing the desired positions, designs and modelings were done PLAXIS2D software and the results were given to experts for better judgement and their comments and feedbacks about the importance of each criterion and evalutaion of alternatives performance in each desired position were received by means of a questionnaireThe results indicated truss retaining structure is the appropriate Selecting for the least deep excavations for all ground types and in more depth grounds Nailing retaining structure and then usually concrete piles are the appropriate alternatives, respectively. The results also depict the excavation depth importance over ground type in this study. This indicates the importance and Significant effect the depth of excavation than type of ground in selecting the appropriate retaining structure in the present study