Time-Dependency and Long-Term Strength of Rocks - Limitations, Interpretation, and Application in Finite Difference Continuum Models
Bibliographic record
Abstract
Many constitutive models have been developed to aid the engineer or scientist in the analysis of material yielding and deformations in the field of rock mechanics. Many of the classical constitutive formulations used are based on instantaneous shearing, or block rotation, but special considerations need to be made when ductile or brittle time-dependent instabilities might arise. These time-dependent effects lead to an accumulation of strains, or even delayed rupture, that cannot be captured using classical constitutive models. The research in this thesis provides an overview of several constitutive models developed for the analysis of time-dependent deformations both at the laboratory and excavation scale. This thesis explores several aspects of time-dependent creep and rupture behaviour for ductile and brittle rocks, respectively. Emphasis is placed on how the different creep material models behave in a numerical model as well as exploring their respective limitations and the effect of boundary and loading conditions on their deformation behaviour. This thesis also further develops the understanding and scientific approaches taken to the testing and interpretation of long-term strength data for brittle rocks. A new proposed methodology and error analysis technique is proposed for analyzing and curve fitting time-to-failure data based on a lower boundary strength limit related to the crack initiation strength threshold. Observations made about the limitations of constitutive creep models and time-to-failure data are used to employ a new numerical model applied at the laboratory and tunnel scale. The model is shown to be able to effectively account for confinement effects in brittle creep as well as capture a pseudo-tertiary creep stage based on simple curve fitting techniques. The work presented in this thesis advances the understanding of the applicability of time-dependent constitutive models as well as provides the necessary framework for practical numerical implementation when analyzing brittle rock failure at the tunnel scale, an important factor for future deep geological repository selection.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".