Examples of ground support practice in challenging ground conditions at Vale’s deep operations in Sudbury
Bibliographic record
Abstract
Vale has operated a number of underground mines in the Ontario division in Sudbury for over a century. During this time, numerous mining methods have been employed including cut-and-fill, drift-and-fill, post pillar cut-and-fill, modified sublevel caving, underhand cut-and-fill/drift and fill plus bulk mining methods such as vertical retreat mining (VRM)/slot-slash, uppers retreat and underhand bulk mining. The division hosts a wide variety of orebodies of varying geometries, many of these at advanced stages of mining extraction. Consequently, the geomechanical challenges are substantial and include both gravity-driven and rockburst-prone ground failure conditions that are further exacerbated by rock mass characteristics and ever-increasing mining depths. Typically the gravity-driven scenarios include the recovery of remnant pillars in old mined out areas, mining through consolidated backfill and recovery of post-failure sill pillars. Burst-prone conditions become a challenge when mining through stiff and brittle geological structures, upon recovery of highly stressed sill pillars in narrow vein ore bodies or when mining at depths in excess of 2,500 m from surface. Gravity driven and stress induced ground failures may occur simultaneously. Underhand cut-and-fill for sill pillar recovery in narrow vein ore bodies are also known to involve risk from both of these failure mechanisms. The adaptation of ground support practices has accelerated over the last two decades leading to an overall improvement in both safety and production. Several cases are presented in this paper illustrating the successful implementation of ground support practices at two of Vale’s six deep mining operations in Sudbury. A particular focus of this paper will be on 153 Orebody of Coleman Mine, where highly stressed multi-sill pillars are being mined by utilising both overhand and underhand cut-and-fill mining method, and 400 and 461 orebodies of Creighton Deep, where mining takes place below 2,400 m from surface. The design and motivation behind the rationale for ground support design are investigated. The equipment, best mining practice and procedures are discussed, as well as products associated with each design.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.007 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.003 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.012 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".