Dynamic properties of sands under cyclic torsional shear
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Bibliographic record
Abstract
Dynamic properties of soils have to be well understood in order to assure stability and acceptable performance of soil structures under seismic and wave loadings. It has been found the two important dynamic properties - shear modulus and damping factor are complex functions of many variables. In order to study the influence of various factors on shear modulus and damping factor, drained cyclic torsion shear tests were carried out in the hollow cylinder torsion device using medium Ottawa A S T M C-109 sand. Effects of shear strain amplitude, stress history, effective mean normal stress (σ'm = l/3(σ-'1 +σ'2 + σ'3)), principal effective stress ratio (R = σ1/σ3), intermediate principal stress parameter (b = σ2 —σ3)/(σ1 — σ-3)), void ratio, number of cycles of loading are some of the factors studied in this thesis. During the application of cyclic shear stress σ'm ,R and b were kept constant at pre-selected values for each test. This technique allows to study the effect cr'm, R and b independently. For example, the effect of R on dynamic properties can be isolated by a series of tests on specimens that have identical σ'm and b but different levels of R and all parameters σ'm, R and b are held constant during cyclic shear application. It is shown that shear modulus increases with number of cycles of a constant amplitude cyclic shear stress when the induced shear strain is higher than a certain threshold value. The damping, however, decreases with number of cycles even at strain amplitudes less than this threshold value. There is also a threshold value of shear strain below which zero volumetric strain occurs due to cyclic shear loading, and hence no pore pressure would develop if cyclic loading was undrained. Effects of stage testing and small strain history on dynamic properties is shown to be insignificant. With decrease of void ratio, shear modulus increases and damping factor decreases. It is shown that for a given b, the void ratio factor F(e) = (2.17 —e)² ( l + e), collapses the modulus degradation curves obtained at different void ratios in to a single curve. For a given initial stress state and shear strain amplitude, shear modulus obtained at different R levels do not show any significant difference when R < 3. Damping factors, however, seems to be unaffected by the change in R at all R levels. When R < 3, shear moduli in triaxial extension condition (b = 1) are found to be less than those in triaxial compression condition (b = 0) and damping factors for b = 1 are higher than those for b = 0. Both triaxial compression and extension state of loadings yielded same values shear modulus and damping factors at large amplitude of shear strain at R = 3. Test results indicate that when b < 1, the dynamic properties are independent of intermediate principal stress. Effects of stress history due to decrease in R from 3 to 2, is significant only in the small strain range, and as the strain level increase, the effects of stress history diminishes.
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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 | 0.000 |
| 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) | 0.000 | 0.000 |
Machine scores (provisional)
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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