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

Document Type : Research Paper


1 Department of Geology, Tarbiat Modares University, Tehran, Iran

2 Department of Civil Engineering, Islamic Azad University-South Tehran Branch, Tehran, Iran.

3 School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.


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.