Haulage drifts play a vital role in providing personnel and equipment access to ore extraction areas for mine production. Thus, their stability is of crucial importance during the life of a mine plan. Many Canadian mines use longhole mining methods or one of its variants. These methods require access to the orebody through haulage drifts on multiple levels. This paper examines the stability of mine haulage drifts with respect to planned mining sequence. A case study of an underground mine is presented. The case study examines #1 Shear East of the Garson Mine in Sudbury, Ontario. A two-dimensional, elastoplastic, finite difference model (FLAC 2D) is developed for a haulage drift situated 1.5 km below surface in the footwall of the orebody. The stability of the haulage drift is evaluated in terms of the spread of yield zones into the rockmass due to nearby mining activities. The performance of the drift stability is evaluated at various mining stages, employing the Random Monte Carlo technique in conjunction with finite difference modelling to study the probability of unsatisfactory performance of the drift. The results are presented and categorized with respect to probability, instability, and mining stage. RÉSUMÉ Les galeries de halage jouent un rôle vital permettant l'accès des operateurs et de l'équipement dans les zones d'extraction . Ainsi, leur stabilité est d'une importance cruciale au cours de la vie de la mine. Plusieurs mines canadiennes utilisent la méthode d'exploitation long-trous ou une de ses variantes. Ces méthodes nécessitent l'accès à la zone minéralisée à travers les galeries de halage sur plusieurs niveaux. Ce document examine la stabilité des galereis de halage des mines en fonction en considérant la séquence minière prévue. Une étude de cas de la zone n ° 1 de cisaillement Est, de la mine souterraine Garson à Sudbury, Ontario, est présentée. Un modèle de différence finie de deux dimensions élastoplastique (FLAC 2D) est développé pour une galerie de halage située à 1,5 km sous la surface (in the footwall of the orebody). La stabilité de la galerie de halage est évaluée en termes de l'extension des zones de rendement dans la masse rocheuse en raison des activités minières à proximité et par rapport à un système de soutien de roche primaire comprenant 2,4 m et 2,1 m de résine coulis barres dans le dos de dérive et les murs de dérive, respectivement . La performance de la stabilité de la galerie est évaluée à différentes étapes de minages , en employant la méthode aléatoire de Monte Carlo en conjonction avec le logiciel de modélisation de différences finies FLAC 2D pour étudier la probabilité d'un rendement insatisfaisant de la stabilité de la galerie. Les résultats sont présentés et classés selon la probabilité, l'instabilité, et l'étape de l'exploitation minière.

Mine haulage drifts are the primary access to the mining blocks of an orebody in a multilevel mining system of a tabular ore deposit. The stability and functionality of haulage drifts are thus crucial to the success of a mining operation. Drift instability could lead to serious consequences such as injuries, production delays and higher operational cost. In this paper, the performance of the haulage drift stability is evaluated on the basis of the primary rock support system comprising 1.8 m resin grouted rebars in the drift walls and 2.1 m long bolt in the back. Two failure criteria namely the extent of Mohr-Coulomb yield zones around the drift, and linear elastic brittle shear failure are adopted and compared, with respect to lower level and same-level mining and filling sequence in the vicinity of the haulage drift. The case study is one of the #1 Shear East zone of the Garson Mine in Sudbury, Ontario. Random Monte Carlo (RMC) technique, which has been previously established to assess the haulage drift stability, is employed in this investigation. The RMC technique is used in conjunction with finite difference modelling software FLAC for random assignment of model input parameters in the FLAC grid. Deterministic model results reveal the drift behaviour in terms of deformation (convergence) and mining-induced stress distribution. Comparison between the two different criteria is carried out to determine which method is most suitable in evaluating unsatisfactory drift performance. The results are presented in terms of probability of instability and categorized with respect to failure condition and mining step. It is shown that the brittle shear failure condition based on linear elastic response calls for enhanced support system at a later mining step than what Mohr-Coulomb yielding condition does. The paper presents a detailed discussion of the stochastic analysis results.

Underground mine developments, such as haulage drifts and cross cuts, play a vital role in providing access to ore extraction areas for mine production. The stability of mine developments is thus of crucial importance during the life of a mine plan. Many Canadian mines use longhole mining methods or one of its variants. These methods require access to the orebody through mine developments such as haulage drifts and cross cuts on multiple levels. This paper examines the stability of mine development access intersections with respect to the planned mining sequence. A case study, the #1 Shear East orebody at Vale’s Garson Mine in Sudbury, Ontario, is presented. A three dimensional, elastoplastic, finite difference model (FLAC 3D) was created for a development intersection situated 1.5 km below ground surface. The stability, or performance of the intersection, is evaluated in terms of the strength-to-stress ratio. The ratio threshold is set at 1.4 for temporary openings. Unsatisfactory performance is defined as a strength-to-stress ratio less than this threshold value. The performance of the intersection stability is evaluated at various modelled mining stages and the probabilistic method of analysis is then invoked to study the probability of unsatisfactory performance of the intersection. The results are presented and categorized with respect to probability, instability, and mining stage.

Mine haulage drifts are the primary access to the mining blocks of an ore body in a multi-level mining system of a tabular ore deposit. Drift instability could lead to serious consequences such as injuries, production delays and higher operational cost. A nonlinear, elastoplastic, two-dimensional finite element model is created to represent typical mining layout most commonly adopted in Canadian underground metal mines. Mohr-Coulomb yielding failure criterion is adopted with respect to lower and same-level mining and filling steps in the vicinity of the haulage drift. The haulage drift stability is evaluated on the basis of the primary rock support system comprising 1.8m resin grouted rebars in the drift walls and in the back. For the purpose of this study, the minimum anchorage length of rock support is taken as 30 cm (12-inch). The drift unsatisfactory performance occurs when the extent of yielding exceeds 1.5m resulting in insufficient anchorage length beyond the yield zone. The probabilistic method of analysis is then invoked to study the probability of unsatisfactory performance of the haulage drift. The results are presented and categorized with respect to probability, instability, and mining stage.

Haulage drifts are the primary access to the mining blocks of an ore body in a multi-level mining system of a tabular ore deposit. Drift instability could lead to serious consequences such as injuries, production delays and higher operational cost. Rockmass properties are significant geotechnical design input parameters. These parameters are never known precisely and always uncertainties associated with them. The stability of the haulage drift is examined through parametric study of a nonlinear, elastoplastic, two-dimensional finite element model representing typical mining layout most commonly adopted in Canadian underground metal mines. The parametric study examines the influence of footwall rockmass geomechanical properties (e.g., cohesion, friction angle, dilation angle and Young’s Modulus) and the mining depth (e.g., horizontal-to-vertical stress ratio). Stability indicators are defined in terms of displacement, stress and the extent of yield zones, which adopt as a basis for assessing the effect of different parameter on the stability of haulage drift.