Crack initiation in clay observed in beam bending
Bibliographic record
Abstract
Tensile cracking in clay is an important phenomenon that affects the strength and permeability of clays in many facilities, such as dams, embankments and landfill liners, as well as being a precursor to slope failures in the natural terrain. This study investigates the stress–strain criteria for cracking in clays by performing four-point bending tests on consolidated kaolin clay beams. Load-controlled and strain-controlled tests were performed on clay beams with varying initial suction to understand the stress–strain criteria for crack initiation in clay. At no stage was the negative pore pressure permitted to exceed the air entry value of the clay, so the clay remained saturated throughout. Strains in the clay were obtained by particle image velocimetry analysis of digital images of the clay beam, and suction measurements were obtained from pore pressure and tension transducers installed within the clay beams. Results from this investigation showed that the threshold tensile strain to cracking in kaolin clay decreased from about 4% at an initial mean effective stress of 15 kPa to about 1·5% at an initial mean effective stress of 100 kPa. The extreme fibre stress at failure of the clay beams indicated an effective tensile strength that was a fraction, dropping from 0·27 to 0·11 of the preconsolidation pressure as the overconsolidation ratio increased from about 2 to about 20. Alternatively, the tensile strength could be regarded as 0·45 ± 0·15 of the geometric mean of the preconsolidation pressure in the plane of shear and the initial mean effective stress. Most significantly, evidence is presented of a new understanding of cracking in clays. Cracks were seen to open either as pure tension cracks at zero minor principal effective stress, or as mixed-mode shear-tension cracks when an effective stress path reaches the Hvorslev criterion of brittle shear rupture, but only if the minor total stress is also tensile.
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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 | 0.000 |
| 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) | 0.002 | 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".