Determination of cemented rockfill strength with large scale UCS tests under in-situ conditions
Bibliographic record
Abstract
Birchtree Mine is an underground nickel mine operated by Vale and located near Thompson, Manitoba. The mining method is sub-level stoping with delayed backfill, with cemented rockfill (CRF) employed as backfill. CRF is composed of sized or un-sized aggregate combined with binder slurry. With proper practice and quality control, CRF offers high strength and stiffness, yielding a stable fill exposure and reducing fill dilution. However, the backfill needs to be economically viable. It is therefore important to adjust and optimize the fill recipe to reduce cost while still attaining the fill strength requirement.The primary goal of the study is to test current CRF practice at Birchtree Mine. The secondary goal is to test adjustments to the current backfill practice to reduce backfill cost. The third goal is to set up a permanent laboratory for the mine to conduct further custom tests as part of a quality control program. To achieve this, the experiment itself needs to be evaluated. Suggestions to improve the experiment, as well as recommendations for future testing, are included in this thesis. The general procedure of the study is described as follows. A literature review was conducted to determine the factors affecting CRF strength. A UCS experiment was then designed based on the literature review. A UCS was designed to conduct the UCS experiment for large scale specimens underground. The experiment was conducted, and the test results analyzed. Finally the experiment itself was evaluated.The factors investigated are cement content, CRF mixing quality, water quality, and aggregate particle size distribution. 27 large scale specimens were prepared and cured under field conditions and tested in the underground lab. The effect of added binder, mixing quality, and grading were determined with respect to the current mine practice taking into account the variation of specimen density. Results for the effect of water quality on CRF strength were inconclusive. An important hurdle the program is the manual preparation of uniform specimens in an underground environment. Consequently, a major shortcoming of the experimental procedure is that specimen particle size distribution (PSD) and moisture were monitored instead of controlled, and specimen uniformity was not achieved with respect to PSD and density. Nonetheless, future tests are recommended, and the laboratory is suitable for the conduct of custom tests. The effects of water content, curing time, and slurry mixing, need to be determined to complete the study. In addition, two-way interactions between moisture content, binder content, and fines content, can be evaluated to optimize the fill recipe.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".