Choosing the accurate slope of open pit, both from the stability and financial point of view, is by far the most vital part of mines design procedure. On the other hand, monitoring systems could be utilized so as to understand the behavior of rock mass. In the current study, slope stability of chador malu open pit was assessed. In this research, various models for both current pit with 50m depth and also final pit have been investigated and the appropriate monitoring systems were recommended.
The stability of natural rock slopes or mine walls is always of great concern in the field of rock engineering. The excavation of jointed rock slopes may cause instabilities and interrupt constructions. In open pit mining, the optimum slope design is usually one that maximizes overall slope angles and minimizes the amount of waste stripping. At the same time, it must effectively manage the risk of overall slope instability, and provide for safe and efficient movement of personnel, equipment and materials during mining operations . There are various methods to analyze and design slopes. These methods include empirical, probabilistic, limit equilibrium and numerical methods. On the other hand instrumentation and monitoring systems could be employed by engineers not only to evaluate real situations of slopes also to inform personnel before occurrence of any instability. Limit equilibrium and numerical analysis techniques have specific advantages and disadvantages inherent in their respective methodologies. Stead et al.  reviewed these methods in detail with respect to their application to rock slope analyses . In this study the limit equilibrium and 2-D distinct element methods have been utilized to design slope of Chador Malu iron open pit mine for present pit with 50m depth and besides for the final pit after 30 years of operations. The purposes of analyses were to gain an insight into the deformation mechanism and stress redistribution of the slope and to investigate the potential failure zones of 30 years pit and to recommend monitoring systems for the mine.
Chador Malu iron open pit mine is situated in 120 km northeast of Yazd city in central Iran. This mine is formed of north and south anomalies. Fig 1 shows the plan view of final pit. According to the initial design, the final pit is like a heart with a width of 960m and depth of approximately 225m. Employing drilling information and simple models, the overall slope angle of 54° and bench slope angle of 70° with a 15m bench height were recommended . Due to complex geology and ground conditions and different geotechnical properties of rock masses and considering the presence of fault and sheared zones, pit walls might have stability problems with the same angle of slope and similar circumstances.
Assessment of rock slope failure mechanisms requires an understanding of structural geology, groundwater and climate, rock mass strength and deformability, in situ stress conditions and seismicity .