A case study on actual water pressure measurements at an open pit excavated in strong, tight rock and the implications for slope design
Bibliographic record
Abstract
Precedent experience is that deep open pit slopes in strong, tight rock masses with high groundwater pressure will not exhibit rock mass failure. The phenomenon is not disputed. It is noted that simple limit equilibrium or finite element slope stability models, often relied upon in mine design and feasibility assessment, can indicate the contrary for high groundwater pressure conditions. In part this is because case history examples on actual groundwater pressure information from this type of open pit are limited. Consequently, over-conservative groundwater conditions can on occasion been assumed for stability analysis purposes. This paper presents a case study of the results of actual measurements of pore water pressure during pit development using vibrating wire piezometers. They were taken for the purpose of addressing risk management concerns over non-conservative stability analysis results for pit deepening and expansion of the Williams open pit at Barrick Gold's Hemlo Operations. The property is situated on the north shore of Lake Superior near Marathon, Ontario, Canada, in an area of moderate hydraulic recharge. The actual drawdown cone was found to be tight to the pit shell at depth, yet broader than expected near−surface. This may have been due to structural features and the interpreted effect of blast damage or the combination of slow excavation and moderate recharge. Site-specific observations are presented in terms of their implications for future slope design at Hemlo and in terms of the groundwater aspect of slope stability modelling in tight rock in general, particularly where limited information is available.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".