Modélisation explicite de l’initiation et la propagation de fractures
Bibliographic record
Abstract
The study of rock mass behavior requires the understanding of their response under various loadings. The study of rock damage from an energetic point of view is essential in order to predict dynamic phenomena. These phenomena are due to the development of cracks in rocks subjected to strong initial and induced stresses. Fracturing is a form of energy dissipation that restores the balance of the involved medium. The aim of the thesis is to model rock cracks and study the behavior of underground structures at great depths. The development of models able to simulate the fracturing, the coalescence of cracks and their interaction with pre-existing fractures is essential. In the literature, there are two main theoretical and numerical approaches for crack modeling: continuous and discrete. A detailed analysis of these approaches has led us to choose the discrete approach and more particularly the code Yade. This code enables to simulate explicitly cracks propagation with or without pre-existing fractures. Developments have been made to evaluate the different forms of energy involved in rock behavior. In particular, a correlation between the cracks energy determined numerically and the microseismic activity observed in laboratory samples has been performed. The various energy components developed and then implemented in Yade are: external work, potential energy, elastic energy, friction energy, cracks energy, kinetic energy and damping energy. Validation of the energy approach was carried out by simulating laboratory tests. The evolution of the various energy components permits to verify that the energy balance is correctly evaluated. The energy balance was also verified at a structure scale by simulating the underground excavation of a Mine-by Experiment (URL Manitoba). The extension of the damaged zone induced by excavation and predicted by numerical simulations was compared with that observed in-situ around the Mine-by Experiment. It has been found that the predicted and the observed damage are similar in the directions of initial minor and major initial stresses. In addition, the energy formulation enables to study numerically the fracturing process of rocks. Wassermann (2006) performed uniaxial and triaxial compression tests on samples of iron ore from Lorraine. We have modeled these tests. The qualitative comparison of acoustic events and cracks energies determined from tests and numerical simulations showed similar trends. On the other hand, the quantitative comparison showed that the number of numerical acoustic events is greater than the number of experimental acoustic events. Also, the energy dissipated by cracks determined numerically is greater than the energy measured in the tests. This difference is explained by sensors accuracy of the experimental device, which are not able to detect all the generated acoustic events. The results obtained will allow us to better understand the dynamic phenomena in the deep underground structures. Another application consisted in modeling an iron ore pillar of Joeuf (Lorraine). The numerical model shows two modes of cracking in the pillar: (a) flaking of pillar wall, (b) two breaking bands initiating from the wall and the roof of the pillar to propagate towards his core. This provides good perspectives for better understanding cracks propagation at a larger scale, also to progress in the understanding of the correlation between geomechanics and geophysics
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".