Integrated risk and stability analysis of an open-pit perlite quarry through numerical modelling

The safety of the slopes during the open pit mining is very important and it not only has a great impact on the safety of the operation but also on the economy. The main purpose of this research was to assess the stability of a perlite mine in Monte Sparau, Sardinia using RS2 and Slope2 software to assess safety factors of the slopes and other geotechnical parameters. The main purpose was to assess the stability of the critical cross sections without reinforcement, to suggest likely failure mechanisms and to assess the overall reliability of the slopes. Perlite is a glassy volcanic rock containing water, which is used in construction, filtration, and other applications that require low density, high porosity and good thermal insulation. The behaviour of the material with respect to slope stability is a function of shear strength, friction angle, cohesion and unit weight- key geotechnical parameters. It is therefore important to know these properties in order to determine the stability of the mine and to ensure that the excavation is safe. Numerical modelling was done with RS2 which is a FEM software by Rocscience, and Slope2 which is LEA based. RS2 was applied to model stress distribution, possible failure surfaces and plastic deformation. Slope2 provided additional FoS values using various failure criteria to those of RS2. The simulation involved establishment of the geological layers, material properties, boundaries and excavation steps that mimic actual slope behaviour. This research concludes that this paper gives a clear picture of the stability conditions of the perlite mine slopes and safety factor values for different parts of the slopes in their natural state. The outcomes of this work can be used to establish the stability of the open cast mine without any reinforcement and therefore in the formulation of recommendations for future excavation planning as well as, if necessary, slope stabilization.