Uncertainties and Complexities of the Geological Model in Slope Stability: a Case Study of Sabzkuh Tunnel

Slope stability analysis is a geotechnical engineering problem characterized by many sources of uncertainty. In slope stability computations, some of these sources are encountered, such as geological details missed in the exploration program, estimation of soil properties that are difficult to quantify and many other relevant factors. Therefore, accurate reproduction of the spatial variability in the field could be essential to decrease uncertainty. The Sabzkuh-Choghakhor water conveyance tunnel is currently under construction using the NATM and TBM tunnelling methods in the Zagros Mountains in south-western Iran. In the slope stability assessment of the Sabzkuh tunnel portal, despite adequate geotechnical investigations, field studies have not been performed with appropriate accuracy. A landslide and collapse has occurred in a part of the portal due to tunnel excavation. In this paper, the importance of having a precise and predetermined schedule for selecting site location, monitoring, complexities of the geological model, uncertainty and its effects on the stability of the trench were investigated and the necessity of comprehensive slope management was emphasized.