Abstract

Abstract
Tunneling construction operations are considered dynamic and complex processes. The success of tunneling construction projects is affected by essential factors. Various methods have been developed in the past, such as simulation models that facilitate and improve the tunneling construction processes and consequently mitigate potential time and cost overruns. Proper selection of excavation method is among the most important factors in tunneling project success. Current practices in selecting the best possible technique for excavation are based on the highest productivity rate as well as the availability of resources. Many of these techniques neglect the interdependencies and concurrency of influencing factors in selecting the best possible excavation method.
In this research, a new method for selecting the most efficient excavation method for tunnels is developed. The method considers a series of significant factors in tunneling construction - namely length, cross-sectional area, geotechnical characteristics depth of the tunnel, and level of water table - and a variety of excavation methods, such as different types of TBMs, Road-header, and drilling and blasting. The factors used in the developed method were constructed based on knowledge extracted from literature and gained from interviews with experts and an online survey. The survey gathered data on the relative importance of the set of selection factors for different soil and project conditions. The collected information was used as input to a developed MCA model (AHP, TOPSIS) that ranked the methods based on their respective suitability for the project at hand to select the most appropriate equipment. The developed method is applied to real case studies to demonstrate its use and highlight its essential features. Also a sensitivity analysis was carried out on each of the case studies, to identify and analyze the most sensitive tunneling variables affecting equipment selection. Based on sensitivity analysis geotechnical condition is the most sensitive factors among all effective variables in both case studies. In the Montreal-Laval Metro Extension, the selected method was Road Header, and in the Spadina Subway project EPB Mixed Shield was selected as the most favorable method of excavation. These results confirm the actually selected excavation methods on the two projects, and indicate that the developed method is reliable.