Technology of an open pit refinement under limit stability of sides

Purpose. To establish the feasibility of refining deep open-pit mines below the boundary of the use of combined motor-conveyor transport with an increased slope angles of the pit walls using the developed transport unit for reloading rocks to overlying horizons during the reactivation of pillars under transport berms. Methodology. Preparation of a digital block model of the deposit, the elaboration of 3D geomechanical models for the dynamics of mining, 2D and 3D numerical simulation of the rock stress-strain state of the outcrops of opencast workings, mathematical modeling of stepwise ore reserves and mining schedule, patent research and feasibility study. Findings. It is advisable to carry out mining in terms of the marginal rock state with an increase in the slope of the pit sides below the limit of application of the cyclic and continuous method in ultra-deep open pits. Such design of pit sides is achieved when benches are mined from top to bottom within the boundaries of steeply inclined layers with the use of inter-bench loaders of the developed designed in the completion zone. Provisions for the selection and feasibility of using the loader in the deep zone are formulated based on demarcation of application zones of cyclic (road transport) and cyclic-flow (combined road-conveyor transport) technologies. Originality. Schematization of the mining operation was performed based on the calculated values of safety factor of sides, which allows increasing the slope angles of the pit walls of even ultra-deep open pits in the completion zone. It was found that with deepening of mining, the zones of potential sliding move away from the loose overburden to lower ore benches closer to the final depth of the Kacharsky open pit (760 m), but the safety factor corresponds to the required value according to the design standards. Practical value. An increase in the slope of the pit walls in the completion zone can be achieved using the developed loading installation, the main difference of which is that it can be moved without dismantling under conditions of reactivation of transport pillars (with an increase in lifting height by 1.54.5 times compared to the known equipment).