Advanced Computational Analysis of Roof Stability in Highwall Phosphate Mining Operations

Abstract:Strip mining is typically preferred for near-surface, tabular deposits such as phosphate. Khouribga, home to Morocco’s largest phosphate deposit, contributs significantly to the nation’s phosphate output. However, a slight dip in the phosphate deposit suggests that strip mining may become less viable in the future. To sustain phosphate production efficiently, transitioning from surface to underground mining through highwall mining could be an effective solution. This method, involving the recovery of phosphate using continuous miners, necessitates stable roof conditions.To evaluate roof stability in highwall mining, both with and without web pillars, we will employ a three-dimensional finite difference method. Firstly, field rock mass properties, including joint frequency, persistency, infills and orientations and mechanical parameters, will be determined for inclusion in the numerical model. The generalized Hoek-Brown failure model, in conjunction with the Geological Strength Index (GSI), will be utilized to analyze rock mass behavior. For intact rock behavior, triaxial tests will be conducted to acquire Hoek-Brown failure parameters. These parameters will inform the construction of realistic 3D models using FLAC3D software, enabling the simulation of various underground working scenarios to identify the optimal mine layout that ensures high production rates and minimizes roof stability issues.An economic analysis will also be conducted to assess the feasibility of this method. This analysis will help in optimizing the dimensions of highwall mining parameters and selecting the best scenario through the Mineable Shape Optimizer (MSO). This planning tool will additionally aid in forecasting the recovery and dilution rates associated with the highwall mining method.