Sample Rocks Tests and Slope Stability Analysis of a Mine Waste Dump

Abstract

The safety and stability of waste dump are vital influencing factors to the mine sustainability and mine employees. Based on a real mine project in a certain open-pit mine waste dump in Tibet, the in situ test on waste rocks from waste dump, including measurements of density, water content, rock size, and natural repose angle, was conducted. Afterwards, these sample waste rocks, of which grain size is less than 5 cm, were selected for indoor large-scale shear test under natural and saturated conditions. By using some engineering methods, the physical and mechanical parameters of waste rocks layer were then determined accordingly. MIDAS-GTS/NX has the advantage of pre-processing modeling. FLAC 3D has good computational and analytical capabilities. The process of dump accumulation is simulated numerically. According to the calculation results of FLAC 3D , the distribution of stress, displacement and plastic zone in the dump is obtained. FOS (factor of safety) for each analytical step in this model was then calculated through the strength reduction method. The limit equilibrium method is used for waste dump stability analysis considering three states: only applied gravity, applied gravity and rainfall, and applied gravity and underground water. The results from this analysis show that the waste dump is stable. The potential failure modes of waste dump mainly consist of the “combined sliding mode” which has circular sliding in upper side and broken line sliding that cuts through gravel-soil layer into heavily weathered layer in the bottom. This paper documents some of the procedures and approaches utilized for waste dump life-of-mine design analysis. It provides reference for further waste dump optimization.