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Numerical modelling is a vital tool in the mining industry and is widely used for planning purposes as well as for examining phenomena on a mine-wide scale. In this paper, a comprehensive rock mechanics study is conducted for the planned mining sequence within an orebody that leads to the formation of a diminishing ore pillar at the Vale Garson Mine in Sudbury, Ontario. A mine-wide numerical model is first constructed in FLAC 3D with input parameters derived from laboratory tests and borehole log data, and is then calibrated based on in-situ stress measurements. The planned mining sequence scenario, comprising mining fronts advancing from the eastern and western sides of the orebody, is examined based on a combined numerical-volumetric analysis. A qualitative assessment of “ore at risk” is first made based on two instability indicators; the brittle shear ratio ( BSR ) and major principal stress ( σ 1 ). In addition, two other sequence scenarios are examined in which mining is accelerated in the east. A quantitative comparison of the results is then made for the three options using the same instability indicators. Based on the optimum sequence scenario, an assessment is conducted of effects emanating from variations in constitutive models and the presence of a shear zone. In the final phase, the BSR and the presence of tensile conditions are used as instability indicators to study the volume of “ore at risk” in stopes adjacent to an opening during a mining stage. It is shown that the proposed methodology, while simple, can nevertheless be a powerful tool for the planning and validation of stope extraction sequence scenarios, and can be used in conjunction with multiple stability indicators. [ABSTRACT FROM AUTHOR]

Haulage drifts in deep hard rock mines require special attention in ensuring their long-term stability and safety, as these drifts must remain functional during the life of a mine plan. The stability of a haulage drift is influenced by many factors, most notably nearby stoping activities and the distance between the drift and production stopes. Thus, the evaluation of drift support performance before and during nearby stope extraction is important. In this study, numerical modelling is performed to evaluate the support performance in the drift. In order to calibrate the numerical model, selected bolts were instrumented with load cells to measure the axial load acting on the bolts as mining progresses. The load distribution along the rockbolt is computed after each mining step. The peak load is found to be consistently at the bolt head in both the fully grouted rebar and the modified cone bolt. It is found that same-level mining of nearby stopes has a more severe effect on the drift support system than lower-level mining. The optimum timing for enhanced support system installation with respect to stope sequencing is also examined. [ABSTRACT FROM AUTHOR]

Mine developments, such as haulage drifts, cross-cuts, and intersections, are the only way to access valuable ore from mining zones; they link mine developments with the nearest ore access points. Thus, they must remain stable throughout their service life or production plan. Mine development instability can cause production delay, loss of reserves, as well as damage to equipment and injury to miners. This paper presents a stepwise methodology to assess the stability of mine development intersections with respect to the mine production plan. A case study, the #1 Shear East orebody at Vale Garson Mine in Sudbury, Ontario, is presented. A three-dimensional, elastoplastic, finite difference model (FLAC 3D) is created to simulate the development of an intersection situated 1.5 km below ground surface. The unsatisfactory performance of the intersection is evaluated in terms of strength-to-stress ratio with respect to mining sequence. A failure criterion is defined by a minimum strength-to-stress ratio of 1.4, and is used for mine developments (temporary openings). The intersection stability is evaluated at various mining stages and the modified 'point-estimate method' (PEM) of (2 n2 + 1) is then invoked to study the probability of drift instability at the intersection. The results are presented and categorized with respect to probability, instability, and mining stage. [ABSTRACT FROM AUTHOR]