Effect of grain size and pore pressure on acoustic and strength behavior of sediments containing methane gas hydrate
Bibliographic record
Abstract
The acoustic and strength behavior of samples containing methane gas hydrate is greatly influenced by the grain size of the host sediment. Tests conducted on clayey silt indicate that Pwave velocity (Vp) may increase abruptly during initial hydrate formation, reaching a maximum of about 2.0 km/s. This is much lower than Vp obtained with Ottawa sand where Vp>3.0 km/s. The samples contained comparable amounts of gas hydrate (pore saturation approx. 21% and 19%, respectively). Although this difference is not totally unexpected, because fine-grained sediment typically has lower acoustic velocities than coarse sediment. Pore pressures in hydrated silt may abruptly change during triaxial shear because the shearing process opens up fluid pathways, and the pressure change is positive as a result of contractive behavior. Contractive behavior induces positive pore pressure response (reduces effective stress) and reduces shear strength. In contrast, dilatant behavior noticed during shear on hydrated sandy sediment reduces pore pressure (increases effective stress) and increases strength. Exploratory drilling or other mechanisms that open pathways between pressured zones separated by gas hydrate could potentially cause marked changes in local pore pressure, even without gas hydrate dissociation. (Author)
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".