Numerical Simulation of a Pit Wall Stability Considering Seismic Impact in Terms of Ultra-Deep Open-Pit Mine

Optimization of the open-pit mine contours can be performed by switching to ore mining with transverse panels within newly cut steep layer. This allows intensifying the ore production and designing the pit wall with a great slope angle. However, an increase in the pit wall sloping angle is associated with the risk of its instability. One of the deteriorating factors is a seismic load providing the additional risk for sliding surface development. A quasi-static approach has been implemented in numerical simulation to consider seismic impact by applying seismic coefficient based on universal macro-seismic scale EMS-98. The intensity of 6 points has been assigned at FEM analysis using RS3 software. At mining stages where the pit wall slope does not exceed 20° the safety factor (SF) lowering due to seismic impact varies in the range from 6.5 to 7.1%. Rising the angle of wall inclination up to 20°–26° makes the slope more vulnerable to seismic impact and the SF drops in the range of 11–13%. The quarry deepening at the final mining stages and increasing the pit wall slope angle up to 30° causes the SF fall in the range of 15–16%. Numerical simulation pointed out the significance of taking into consideration the seismic component, since, together with other deteriorating factors (the presence of faults, fracturing), an additional horizontal load brings the pit wall stability to a critical level.