Open Collections

Reyes, Andres

University of British Columbia

Seismic liquefaction-induced displacements present a significant threat to geostructures and civil infrastructure, underscoring the need for accurate predictive tools in earthquake engineering. This doctoral thesis focuses on validating and enhancing the SANISAND soil constitutive models to effectively address these displacements and contribute to advancing of performance-based earthquake engineering. The validation of the SANISAND class involved assessing its accuracy in predicting shear-induced volumetric responses in soil deposits subjected to bidirectional seismic shearing. Dynamic centrifuge tests on homogeneous soil deposits served as the benchmark, revealing the model's commendable capability in estimating seismic liquefaction responses. Subsequent simulations explored the contrasting impacts of bidirectional and unidirectional seismic shearing, enriching the understanding of soil behavior under different conditions. Further validation efforts targeted simulating soil liquefaction and surface lateral displacements on sloped ground and in systems with liquefiable deposits supported by sheet-pile walls, drawing insights from dynamic centrifuge tests on liquefiable sand deposits. The numerical models provided reasonable estimates of the seismic liquefaction response. Crucially, the calibration process required considerations for initial shear stresses. This exhaustive validation approach ensured a comprehensive understanding of the model's applicability in diverse scenarios, emphasizing the importance of capturing the influence of initial shear stresses on undrained cyclic shearing responses at the constitutive level. Given the imperative of accounting for initial shear stresses' effects at the constitutive level, the SANISAND class was extended. This extension involved modifying the constitutive model named SANISAND-MSf. The primary enhancement of this model was the introduction of a novel internal state variable, augmenting plastic stiffness and dilatancy to simulate residual deformation accumulation observed in undrained cyclic shearing without stress reversals. Additional refinements to the memory surface and semifluidized state formulations addressed accurate control of plastic stiffness and reduced plastic shear stiffness, crucial for replicating large cyclic strains during cyclic mobility. Validation efforts for the modified SANISAND-MSf model included laboratory experiments on various sand types and centrifuge tests, underscoring its potential in real-world applications. This refined constitutive model significantly contributes to the field of performance-based earthquake engineering, offering an advanced tool for predicting seismic liquefaction-induced displacements and enhancing our understanding of soil behavior in earthquake scenarios.

Text

2025-01-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87250

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/