Stress-strain-strength Behavior of Ottawa Sand in Direct Simple Shear
Open AccessThe stress-strain-strength behavior of sands is of significant interest in investigating the phenomenon of soil liquefaction that is the cause of extensive damage to civil infrastructure systems. This thesis intends to assess the stress-strain-strength behavior of Ottawa F-65 sand through laboratory experiments and numerical simulations. The laboratory experiments include a series of stress-controlled monotonic and cyclic direct simple shear tests conducted at vertical stresses of 40 kPa and 100 kPa to investigate the stress-strain-strength response of Ottawa F65 sand under different monotonic and cyclic shear stress loading conditions. The lateral stresses that develop in direct simple shear tests are evaluated through an upgrade of the direct simple shear equipment to include 3D printed confining rings embedded with fiber optic sensors. Parallel to the experimental campaign, a series of nonlinear finite element simulations are conducted to assess the suitability of direct simple shear tests to obtain the stress-strain-strength response of soils. These simulations specifically evaluate the effects of boundary conditions and system compliance. Motivated by the overall consistency of the experimentally observed response of the soil, an Artificial Neural Network (ANN) model was trained on the dataset collected from extensive laboratory experiments for a specified set of normal stresses, cyclic stress ratios, initial shear stresses and relative densities. The performance of the ANN model was then assessed by conducting blind predictions of the stress-strain-strength response of Ottawa F65 sand under a new normal stress and a new soil relative density. Cyclic direct simple shear tests conducted at the same density and normal stress used in the blind predictions were then carried out to validate the model performance.
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