Numerical modeling of rock spalling in the mine-by experiment, using zero-thickness interface elements with a fracture-based visco-plastic constitutive model
Bibliographic record
Abstract
The precise extent and opening of cracks and fractures in the rock mass around waste disposal facilities is an important element of concern because of the potential detrimental effect on the effective long term sealing of the repository. This is the main motivation for this study, focused on the rock spalling observed in the Mine-by test tunnel of the AEC laboratory (Canada), located at a depth of 420 m in the massive brittle granite of Lac du Bonnet, where high horizontal initial stresses have led to significant spalling which has been widely documented in the literature. The present numerical study is based on the FEM with zero-thickness interface elements (FEM-z). These elements are equipped with an energy-based work-softening constitutive model incorporating Fracture Mechanics parameters. The model is implemented in two versions: elasto-plastic and visco-plastic. Viscoplasticity is used primarily as a numerical tool in the context of the visco-plastic relaxation strategy, although it also opens the door to considering the physical time evolution of fractures and spalling as observed in the field. The procedure developed includes one or more excavation stages, each of which consists of removal of elements and application of the corresponding contact forces, which leads to stress redistribution around the excavated area and potentially to opening/sliding of existing or new cracks. A first excavation involves the tunnel cross-section. Additional excavation stages may be necessary to remove continuum elements or blocks that become completely surrounded by open cracks as the result of previous excavation stages. The methodology is applied to the Mine-by case. The results obtained show that the procedure employed is capable of leading to the observed spalling using parameters and assumptions which are in agreement with the information available for the site.
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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 | 0.000 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".