Sensitivity Analysis of Mechanical and Geometrical Properties of Fly Ash Stabilized Overburden Dumps Using Mathematical Simulations

Abstract

Increasing stripping ratios in surface mines have led to the removal and movement of huge volumes of overburden that is generally stored in form of internal or external dump within the mine boundaries. For safe storage in limited areas, the overburden dumps are stabilized using several popular methods. One of the recent economic and environmentally safe techniques is the stabilization of dumps using fly ash composite material. This study analyzes the sensitivity of the overall stability of the dump slope on its geometrical and material properties, when stabilized using fly ash composite. Four different geometric parameters and six material properties were varied in simulated dump models to find the sensitivity of the factor of safety (FOS) using limit equilibrium (LEM) and finite element methods (FEM). The sensitivity analysis was also carried out for minimum thickness of fly ash composite layers required for better stabilization of dump slopes. From the study, it was observed that FOS of the dump slope was most sensitive to the material properties of overburden, apart from the slope angle, dump height, number of fly ash layers, and cohesion of fly ash composite (Sensitivity Index (SI) > 0.2), while it was less sensitive to other geometrical parameters and material properties. The critical composite layer thickness was found to be most sensitive to all the geometrical parameters, but very less sensitive to the material parameters (SI < 0.1). These sensitivities give a clear idea of the criticality of various parameters for a stable dump slope design.