Risk-Based Decision Making Method for Selecting Slope Stabilization System in an Abandoned Open-Pit Mine
Mahnoush Gharehdaghi1, Hesam S. Tehrani1, Ali Fakher2, *
1 School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran
2 Department of Civil Engineering, University of Tehran, Tehran, Iran
The construction and stabilization of deep excavations are associated with several uncertainties due to heterogeneous geological conditions. Therefore, the conventional methods of slope stability analysis do not provide reasonable results.
Hence, it is logical to perform reliability analysis and also risk assessment to make a wiser decision under uncertainty for choosing the proper stabilization method of slopes.
In this regard, a real case study, a 50-meter-deep abandoned open-pit mine, is considered. In the past, the studied deep excavation was located in a rural area, away from the important structures. However, due to the development of the city, the open-pit mine is now located in the city. Furthermore, the Kan River is located on the eastern side of the excavation. Deterministic analysis showed that that Factor of Safety is not sufficient for permanent condition; thus, the deep excavation may have destructive impacts on the adjacent structures and infrastructures by putting them in danger in the case of failure.
These circumstances resulted in using reliability analysis and risk assessment using non-deterministic approach. Random Set Finite Element Method (RS-FEM), a non-probabilistic method, is used in determining how much the slope is reliable. The upper and lower bounds of probability of excessive displacement and probability of failure are obtained using RS-FEM by Plaxis2D software. Afterward, HAZUS is successfully used to quantify the economic risk of different stabilization alternatives by defining various scenarios in order to consider the consequences of excavation failure on adjacent utilities and infrastructures.
The best alternative is defined as the stabilization method with the lowest economic risk. As a result, it is noticeable that this paper provides a comprehensive methodology for decision making, based on reliability analysis and risk assessment, in stabilizing slopes.
Keywords : Deep excavation, Open-pit mine, Slope stability, Reliability analysis, Random set, Finite element, Risk assessment.
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* Address correspondence to this author at Department of Civil Engineering, University of Tehran, Tehran, Iran; Tel: +98 9123380360; E-mail: Afakher@ut.ac.ir