The depth of open pit mines has augmented in recent years. Therefore the risk of large-scale slope instability has increased. The slope stability of open pit is by far the most critical factor in the life of the mine. In addition, dynamic loads can reduce the stability. On the contrary; engineers have been utilizing various numerical methods in order to understand the behavior of the rock masses. In the present study, the stability analyses of Chador-Malu iron open pit mine under static and dynamic loads have been carried out. This mine is located 120 km northeast of Yazd city in Iran with a maximum height of 225 meters. In the first step, earthquake hazard analyses have been reviewed and in the second step, the static and pseudo-static stability of the slope by employing the limit equilibrium technique have been determined. Afterwards the static and dynamic responses of the slope by using two-dimensional distinct element methods have been assessed.
The stability of natural rock slopes or mine walls is always of great concern in the field of rock engineering. In open pit mining, the optimum slope design is usually one that maximizes overall slope angles and minimizes the amount of waste stripping [1]. There are various methods to analyze and design slopes. These methods include empirical, probabilistic, limit equilibrium and numerical methods. In this study the static and dynamic analyses of Chador- Malu mine for the final pit after 30 years of operations have been performed by using the limit equilibrium and also the Universal Distinct Element Code (UDEC).
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. 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 [2].
Chador-Malu mine has a complicated condition due to tectonics activity and complex geology situations. Five geotechnical domains have been defined based on various parameters. Figure 2 shows various geological units and five geotechnical domains of pit. The southwest section of the mine which is positioned in the third geotechnical domain, would reach to the final pit wall sooner than other sections. Summary of the rock mass properties for the third domain are tabulated in Tables 1. The rock mass quality of southwest sector of the mine is generally poor to fair and varies from very poor to fair [3].
The assessment of seismic response of structures requires an understanding of the anticipated ground shaking as well as an evaluation of the response of the ground and the structure to such shaking [4]. The probability of large magnitude earthquake occurrence is high in the site area. Deterministic and probabilistic approaches have been used to assess the likely maximum horizontal ground accelerations at the site, for return periods of 20 and 50 years.
