Effects of pore collapse and grain crushing on ultrasonic velocities and <i>V</i><sub><i>p</i></sub>/<i>V</i><sub><i>s</i></sub>
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Compressional, shear wave velocities and their ratio, V p / V s , were measured along with porosity variations during wet and dry hydrostatic compaction of Bleurswiller sandstone, a 25% porosity Vosgian sandstone. At first, increase in hydrostatic pressure was accompanied by a simultaneous increase of both V p and V s as expected. At a critical effective confining pressure P *, a large mechanical decrease of porosity was observed that was due to pore collapse and grain crushing. Theoretically, two different processes are affecting the elastic wave velocities in counteracting ways during cataclastic compaction: cracking and porosity decrease. Our experimental results show that cracking is the dominant effect, so that grain crushing and porosity reduction were accompanied by a large decrease in velocities. The ratio V p / V s was also observed to change during our experiments: In the wet specimen, V p / V s value increased from 1.72 to 1.84, while in the dry specimen, it increased from 1.59 below P * to 1.67 beyond P *, respectively. To quantitatively interpret these results, an isotropic effective medium model (EM) was used that considered the sandstone as a mixture of spheroidal pores and penny‐shaped cracks. In particular, the increase in V p / V s , in the wet case, is well reproduced and shows the important role played by the mechanical coupling of fluid with low aspect ratio cracks (<10 −2 ). In the dry case, however, our experimental results highlight an increase of V p / V s ratio during cataclastic compaction, in apparent contradiction with the predictions of the EM model. Indeed, increases in V p / V s ratio, and hence in Poisson's ratio, are, in general, attributed to fluid saturation. A closer look to the microstructure may provide a possible interpretation: Beyond P *, grains are no longer cemented. Using Digby's granular model as an alternative model, we were able to reach a quantitative agreement with the experimental results. The possible implication is that in both dry and wet conditions, cataclastic compaction due to grain crushing induces an increase in V p / V s ratio.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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 it