Fuzzy analysis and risk management of water inrush by numerical simulation and FMEA under uncertainty condition for Emamzade Hashem tunnel

 Tunneling under the water table is a compatible condition for projects. Most important consequences of tunneling in this situation are water inrush, bad working condition, mudflow, low advance rate, and humans injuring. Especially for TBM tunneling that required high investments funds, these hazards can impose high costs for a project. This paper estimates water inflow by the finite element method in the second part of Emamzade Hashem tunnel and providing risk management for these hazards using the FMEA method. 

The second part of Emamzade Hashem tunnel is the longest road tunneling project in Iran that will be excavated by a TBM. TBM tunneling in hard rock and faulty zone have lots of hazards that may cause many stops in the project according to previous similar projects around the world. Risk management could classify hazards and make them predictable and controllable.

In this paper, water flow ratio was estimated by numerical simulation with FLAC 2D. In the following, the classical risk of water inrush was calculated by the FMEA method with studding some similar projects. A fuzzy analysis was then applied to increase the accuracy of the results. To this end, after estimating water inflow for each section of the tunnel, the time and costs of each hazard were calculated by studying similar projects. Risk number was estimated and managed through the FMEA method based on the calculations. The reduction actions were suggested for the hazards with high-risk numbers.

The results of the study indicated that tunneling in the middle part of the tunnel has high risk due to high water pressure according to classical and fuzzy analysis. It has resulted that the performance of fuzzy analysis is higher than classical analysis.