The stressstrain behavior of Ottawa F65 sand is investigated through an extensive series of constant volume stresscontrolled cyclic direct simple shear (CDSS) tests performed at different densities, overburden pressures, and static shear stresses prior to cyclic shearing to quantify their effects on the cyclic strength of Ottawa F65 sand. Results of the CDSS tests are used in the constitutive model calibration exercise for the Liquefaction Experiments and Analysis Project (LEAP2022). The collected database of CDSS tests is used to develop an Artificial Neural Network (ANN) model capable of predicting Ottawa F65 liquefaction strength for a specified set of relative density, overburden pressure, static shear stress ratio, and cyclic shear stress ratio. After training, validation and testing, the ANN model is further assessed using blind prediction of the liquefaction strength in new CDSS tests for a relative density and overburden stress that are not available in the training dataset. CDSS tests under similar conditions were then carried out in the laboratory for validation of the ANN model. The comparisons of the predictions with the experimental results have demonstrated the ANN model predictive capability for liquefaction strength and its sensitivity to changes in relative density, overburden stress and cyclic stress ratio.
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Effect of shear strain rate on undrained shearing resistance of a clean silica sand measured in direct simple shear tests.
A number of studies examining the effect of shear strain rate on undrained shearing resistance of clean sands using conventional laboratory tests have been reported. Constantvolume direct simple shear laboratory tests were performed to model flow displacements at various shearing rates after triggering flow liquefaction. Tests on clean sand (Ottawa F65 sand) at shear strain rates of 0.1%/min and 10%/min illustrated that the undrained yield (peak) shear strength at a shear strain rate of 10%/min was about 14% greater than that measured at a shear strain rate of 0.1%/min, while the undrained criticalstate shear strength is relatively independent of shear strain rate for the shear strain rates (0.1%/min and 10 %/min), sand type, and initial state considered in this study.
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 Award ID(s):
 1728199
 NSFPAR ID:
 10406481
 Date Published:
 Journal Name:
 Tailings and Mine Waste '20
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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The stressstrain behavior and liquefaction strength of Ottawa F65 sand was investigated through an extensive series of cyclic direct simple shear (CDSS) tests. The study quantified the effects of static shear stress on the cyclic strength of Ottawa F65 sand. The database of CDSS tests was used to develop an Artificial Neural Networks model to predict Ottawa F65 cyclic strength.more » « less

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