Required strength evaluation model and its application for vertically exposed backfill: inspired by Mitchell’s physical model tests
Bibliographic record
Abstract
Cemented paste backfill is an increasingly popular technique to improve ground stability in underground mines. This technique is used in several mining methods that require strength evaluation for the vertically exposed cemented backfill following the excavation of an adjacent stope on one side. The critical strength is generally evaluated with an analytical solution proposed by Mitchell et al. (1982). Despite its wide acceptance in academia and application in the mining industry, the Mitchell solution has received only a few updates in the literature, including some new developments given by the authors and colleagues. The original Mitchell solution and its variants were mainly validated against the physical model test results obtained by Mitchell et al. (1982). Even though the Mitchell model debatably assumed a zero backfill friction angle, the required strengths predicted by the Mitchell solution corresponded quite well to those obtained by physical model tests. This study reanalysed the Mitchell solution and its physical model. The testing conditions and procedures for measuring the shear strength parameters are investigated. The stability of the cemented backfill upon removal of a confining wall is analysed with FLAC3D. The comparisons between the numerical modellings, experimental results and analytical solutions are presented, and the applicable range of the classical Mitchell solution is discussed. A new analytical solution is proposed to evaluate the minimum required strength of the cemented backfill confined by two sidewalls exposed on one side and subject to pressure from uncemented backfill on the opposite side. The proposed analytical solution is validated by numerical simulations with FLAC3D. The proposed analytical solution is used to determine the theoretical strength requirement of cemented backfill in primary stopes of an iron mine that employs stage stoping with subsequent backfill mining. The floating Factor of Safety (FS) characterising the current backfilling quality control level of this mine was statistically evaluated with a large amount of uniaxial compressive strength (UCS) data after testing vast drilled samples from field stopes. The engineered strength requirement of the cemented backfill in primary stopes had been finalised by combining the analytical results and floating FS of the mine.
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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".