Instability risk assessment of open cut trenches of Sungun copper mine by FAHP

The optimum operation of an open pit mine needs special attention to geotechnical problems including slopes stability. Such investigations should be performed continuously, and the obtained results be used in mine designing and also development studies. There are various types of factors affecting the instability problems of mine slopes and should be identified and investigated during risk assessment process. In this research, an attempt was made to identify the most important factors related to instability of slopes of Sungun copper mine, then rank factors based on their importance. For this purpose, Fuzzy Analytical Hierarchy process (FAHP) has been used. At first, using a questionnaire experts were interviewed and on this basis the most important risk factors defined in 3 layers, then the Hierarchal structure of problem was drawn. Then, FAHP was used to calculate the relative weight of factors affecting risk of slope instability and to determine their importance. The results obtained of field studies and also long term plans for slope controlling were compared with FAHP method results. On this basis, delay in mining operations (Layer 1), extended failure (more than a bench) (Layer 2), and discontinuities (Faults & Joints) (Layer 3) were defined as factors with high importance during risk assessment of slopes instability of Sungun copper mine.