Investigation of Softening Instability Phenomena Under Simulated Infinite Slope Conditions in Centrifuge Tilting Table Tests
Bibliographic record
Abstract
Element test results reported in the literature under both triaxial and plane strain conditions indicate that loose saturated granular specimens can experience softening instability at stress ratios lower than what might otherwise be expected given the critical state friction angle of the soil.The region of potential softening instability in stress-space is often explained using the framework of the instability line.This phenomenon is particularly relevant to shallow slopes of 1 to 2 m depth.However, the practical realities of sample preparation for triaxial testing make performing tests below 20 to 30 kPa of confining stress exceptionally difficult.In this thesis, the development of a centrifuge tilt-table test device is described which aims to test the behaviour of loose granular slopes under stress paths of increasing slope inclination or increasing pore water pressure.A system of instrumentation including pore pressure transducers, inclinometers, displacement transducers, and high-resolution cameras was designed to monitor the behaviour of the slope model.The development of a system to provide a controlled groundwater level within the slope model proved to be particularly challenging.The results of two competing design concepts are presented for the water boundary condition and discussed.The centrifuge tilt-table is used to compare the physical response of a slope to the behaviour predicted by the infinite slope and softening instability models using scale model centrifuge testing.If softening instability is a rigorous concept, it should be the primary observed failure mechanism as it will occur at a stress state below the failure line.Tests were performed on loose Ottawa F110 sand at 1g, 20g and 40g and 60g.Deviatoric strain-softening was observed in loose dry sand.The softening instability event resulted in a rapid increase in shear strain at constant shear stress while the soil was at a stress state below the failure envelope.Any soil that can experience softening instability (i.e.granular, loose, saturated, and behaves undrained) will iii undergo two failures: one caused by deviatoric strain-softening (softening instability) and a second caused by shear failure at a larger slope angle.
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How this classification was reachedexpand
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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".