Biaxial gradient loading approach with unilateral constraint for testing dilatancy behavior of narrow coal pillar in gob-side entry driving
Bibliographic record
Abstract
The stability of narrow coal pillars is critical for gob-side entry driving (GED), particularly regarding their dilatancy behavior under gradient loads from lateral roof rotation and subsidence. However, few studies have considered the actual stress environment and boundary conditions. In this study, a biaxial gradient loading approach with unilateral constraint was proposed. A corresponding polymethyl methacrylate-steel test device was designed, and the effectiveness of the strategy was verified. Subsequently, biaxial uniform and gradient loading tests with unilateral constraint were conducted on coal samples at different lateral roof rotational angles. Compared with uniform load, coal samples under gradient load exhibited localized failure, with a decrease in compressive strength of 20.87%–54% and a reduction in acoustic emission (AE) energy. Asymmetric dilatancy was significant, with dilatancy stress decreasing by more than 50.48%. The mass of fragments smaller than 20 mm decreased by 81.85%, while fractal dimensions exceeded 2. As the stress gradient increased, localized failure intensified, with compressive strength and AE energy first decreasing and then increasing. The compressed state gradually disappeared, leading to direct dilatancy deformation. The mass of fragments larger than 20 mm increased by 101.37%, and fractal dimensions first increased and then decreased, peaking at 2.55. Moreover, the dilatancy instability mechanism induced by the stress gradient was revealed, and the method for identifying the dilatancy patterns was proposed. The applicability and limitations of the test approach were finally discussed. This study is crucial for accurately understanding and predicting the dilatancy instability of the narrow coal pillar in GED.
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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) | 0.001 | 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 | 0.001 |
| 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".