Slope stability analysis of an open pit mine with considering the weathering agent: Field, laboratory and numerical studies

Freezing-thawing (F-T) processes can affect the slope instability of open pit mine wall in cold regions, resulting the increase of mining operations cost and decrease the safety of personnel and equipment. Therefore, estimating the degradation of rockmass geomechanical properties under the weathering agent is crucial for slope stability analysis of an open pit mine in mountain areas. Accordingly, for optimal slope stability analysis of Angouran open-pit mine in this research, variations of physico-mechanical properties of pit wall schist rock including dry density, and uniaxial and triaxial compressive strengths were firstly measured during the defined F-T cycles. Then, the related properties of slope rock mass were determined using the generalized Hoek-Brown criterion. Based on the estimated rock mass characteristics, a numerical model of mine slope was constructed and pit stability conditions was analyzed. According to the obtained results, the displacement of slope rock mass varied from 0 to 14.6 m, occurred in highly weathered schist, indicating the low probability of large collapses. To validate the achieved results, 30 prisms were installed in the north-west wall of mine and in-situ displacements were recorded three times in week for one year. Results indicated that the measured displacements from in-situ monitoring and numerical model are in good agreement, so that the determination coefficient (R2) was obtained 0.80.