Sergo Ordzhonikidze Russian State Geological Prospecting University, Moscow, Russia:

L. A. Yarg, Professor, Doctor of Geologo-Mineralogical Sciences
I. K. Fomenko, Professor, Doctor of Geologo-Mineralogical Sciences

Stary Oskol Division, Sergo Ordzhonikidze Russian State Geological Prospecting University, Stary Oskol, Russia:
O. M. Zhitinskaya, Lecturer, gonjarova_o@mail.ru

Open pit mining of the Stoilensky iron ore deposit entails extraction of huge volumes of overburden and ore and radically changes stress–strain state in subsoil. The long-term operation (50 years) of the nature-and-technology system (NTS) at Stoilensky Mining and Processing Plant has altered ranges, regimes and sets of influential processes. With respect to the negative effects, the interaction sphere inside NTS can be divided into 5 zones: aerodynamic impact; process water seepage (spreading dome); slurry differentiation (stratification and sludge settling); migration of chemicals; compaction, suffusion and gravity processes (slides, falls, landlsides and mudflows). Thereupon, it is possible to substantiate the most informative parameters to be monitored. The ultimate pit limit is reached in the sedimentary cover overlying the uneven ore crystal basement. This study estimated influence factors of slope stability for Stoilensky open pit mine to ensure its stable operation in the sedimentary cover rock mass. Optimization of NTS performance is based on the modern design procedure for pit wall slope stability. This study involved: 1) the method of limit equilibrium with Slide7, Slide3D (Morgenstern–Price and simplified Bishop and Janby); 2) FEM with Rocscience RS2, which is a class of numerical methods recommended for the current regulatory documentation applications. The pit wall slope stability was modeled in two schemes: local stability calculus with the minimum stability coefficient (Кs) for pit wall; global stability assessment. The global pit wall stability was calculated using both the methods of limit equilibrium (in 2D and 3D formulation) and finite elements. The variability patterns of the geological engineering environment components are the basis to set certain limit parameters for Stoilensky open pit mine such that the long-term operating system is never beyond the allowable ranges. This includes assessment of the pit wall stability coefficient with regard to induced change in state and strength of the pit wall rock mass, dynamics of groundwater and additional load on pit walls from overburden dumps.

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