INTERNATIONAL CONFERENCE ON MANAGEMENT (ICM 2011) PROCEEDING 1219 RISK EVALUATION OF TUNNELLING PROJECTS BY FUZZY TOPSIS Mohammad Majid Fouladgar 1 , Abdolreza Yadani-Chamzini 1 , Mohammad Hossein Basiri 2 1 Fateh Research Group, Tehran, Iran; manager@fatehidea.com 2 assistant Professor of Tarbiat Modares University, Mining department, Engineering Faculty, Tehran, Iran Risk factor in tunnelling projects is so important. This factor can be effect on at least one project objective such as time, financial, and quality. So, this factor is critical for managers or planners, so that; they always look for an appropriate method in order to prioritize the existing risks. There are miscellaneous techniques for evaluating and ranking risks such as Delphi technique, multi criteria decision making (MCDM) methods, and fuzzy logic. The MCDM methods are suitable tools to solve sophisticated problems in real world. TOPSIS approach is one of the most application MCDM methods. On the other hand, fuzzy logic is a helpful tool in the presence of uncertainty and complexity. In this paper, we applied TOPSIS approach under fuzzy environment in order to evaluate the existing risk in water transfer tunnel project of Dashte Zahhab. The results demonstrate collapse is the riskiest parameter. Field of Research: Decision Making, Fuzzy Set, Risk Management, Tunnelling 1. Introduction Risk evaluation is a part of risk management which can help decision makers to rank the existing risks, and finally, the appropriate reaction is accomplished. There are various techniques for evaluating risk such as Monte Carlo Simulation (Rezaie et al, 2007; Au et al., 2007; Wu, 2008; Amigun et al., 2011), Event Trees (Linder et al., 1987; Meloy, 2006; Vílchez et al., 2011), Fault Trees (Lindhe et al., 2009; Ferdous et al., 2009; Vaurio, 2010; Farret et al., 2011), Failure mode and Effective Analysis (Carlsson, 2004; Gowland, 2006; Wang et al., 2009; Leeuwen et al., 2009; Hu et al., 2009; Xiao et al., 2011; Zhang & Chu, 2011), Fuzzy set (Chen & Chen, 2008; Lee & Chen, 2008; Chen & Wang, 2009; Feng & Luo, 2009; Xu et al., 2010; Hejazi et al., 2011; Idrus et al., 2011). Due to the critical importance of risk in underground construction, different researches are accomplished in order to evaluate and assess risk. Sari et al. (2009) proposed a methodology towards development of an uncertainty model that includes randomness in the occurrence of days-lost accidents in a coal mine. Their study showed that stochastic model estimates that although, there would be substantial reduction in the expected number of accidents in the near future, the higher level of risks still should be a concern for the mine management.