Open Collections

Palmieri, Francesca

University of British Columbia

Cyclic loading influences the strength and deformation characteristics of clayey soils depending on the applied cyclic shear level. Earthquakes, waves, wind and traffic are just some of the many sources inducing cyclic shearing of variable amplitudes. For all related applications, this dissertation is relevant as it provides: i) an analytical procedure for the prediction of the cyclic strength under different levels of cyclic stress ratios (CSRs), and ii) a constitutive model capturing the stress-strain response during undrained cyclic shearing of different amplitudes. The analytical procedure was developed based on the analysis and interpretation of published experimental data on various clayey soils. Based on this study, a material parameter quantifying the effect of CSR on the cyclic strain accumulation was identified and reasonably linked to the soil index parameters. In parallel, the phenomenon of cyclic failure was investigated and a specific failure criterion was proposed based on the evolution of the accumulated strain with cycles. The detected material parameter and suggested failure criterion were adopted in the proposed procedure to predict the cyclic strength of clayey soils under any static shear stress and frequency. The predictive capabilities of the analytical procedure were validated against data of two clays. An advanced bounding surface rate-independent plasticity model for the cyclic response of clays was developed based on a previous SANICLAY model version. The peculiarity of the proposed model lies in its capability of triggering the stiffness and strength degradation based on a novel internal variable that serves as a proxy for the applied cyclic stress level. By defining a threshold of this internal variable, the proposed model can capture the existence of the cyclic stress and strain thresholds characterizing the response of clays subjected to undrained cyclic shearing at different amplitudes. Validation of the model formulation was restricted to the simulations of symmetrical two-way undrained cyclic loading in both stress amplitude-controlled triaxial and strain amplitude-controlled simple shearing. Results show that the proposed model can successfully capture the stress-strain response of clays subjected to various cyclic loading amplitudes with a unique set of model parameters, for which a step-by-step calibration guideline is also provided.

Text

2024-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/81352

Civil Engineering

University of British Columbia

UBCV

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