Mining operations and geotechnical issues in deep hard rock mining – case of Boukhadra iron mine

Underground mining operations are a very problematic task, especially in poor geotechnical conditions. The right choice of excavation and support techniques leads to adequate and secure mining operations. This should ensure the overall stability of the underground mine with the best productivity and stability performance. In this paper, an empirical model for obtaining support systems for underground galleries was applied. Then, a numerical model for the evaluation of the performance of support measures for rock masses in the Boukhadra iron mine was introduced. Extensive field and laboratory tests were performed to obtain geological, geotechnical, and mechanical data on the entire geologic formations of the (1105 m) level. The performance of the design is supported by the selection of a common support plan between RMR, Q, and UBC systems for each geotechnical unit. Therefore, the rock masses classification based on the geo-mechanical model has determined the suitable support systems. The finite element model (FEM) was used for the analysis of rock mass behaviour, displacements, stress, and plastic point distribution. The results permit the optimization of the plastic zone thickness around the gallery. The outcomes of this study could improve the stability of the mine by choosing the right direction of excavation in consideration to the direction of the discontinuity planes. In order to choose between the current and the recommended mining operations, an equivalent calculation sequence was verified. Our study demonstrated that the consideration of discontinuity sets in the orientation of excavation highly improves the mining conditions with or without support