A new method for selection of optimum tunnel excavation method based on multi criteria decision making

Selection of tunnel excavation method is one of the most important issues raised in the tunneling projects Because experience has shown that the results of incorrect choice of excavation method can lead to catastrophic situations. Various parameters are effective in choosing the right option for excavation a tunnel. The most important parameters include geological and geotechnical, geometric, executive, economic parameters and parameters related to infrastructure and necessary conditions for tunneling methods. in this research, a model for comprehensive evaluation and selection of the most suitable tunnel excavation method from the methods of drill and blasting, controlled drill and blasting, cut and cover, Austrian drilling method, road header machine and conventional shield excavation (TBM) is presented.In this model, after studying and reviewing the relevant topics, the indicators that are effective in evaluation were considered and since the importance of the indicators in the evaluation is not the same, a questionnaire was prepared to determine their weight and their weight was determined by aggregating the opinions of experts. Scoring for each of the indicators for each of the excavation methods was done by evaluation questionnaires containing questions in numerical quantification. Finally, the simple weighting method (SAW) was used hierarchically to calculate the final score of each method. In this method, according to the geological and geotechnical conditions and the geometric parameters of the existing tunnel, the score of each index is multiplied by the final weight of that index and from the sum of them, the final score of each method is obtained. Finally, the method with the highest score is selected as the appropriate excavation method.