Graduation Semester and Year

Spring 2026

Language

English

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering

Department

Civil Engineering

First Advisor

Xinbao Yu

Second Advisor

Laureano R Hoyos

Third Advisor

Himan Hojat Jalali

Abstract

This study presents an integrated experimental and numerical investigation of the stress–strain behavior and shear strength characteristics of reconstituted kaolin clay prepared using a slurry consolidation technique. The primary objective is to evaluate the influence of stress history, testing methodology, and strain level on the mechanical response of soft clays, and to assess the applicability of advanced constitutive modeling for reproducing observed behavior.

Uniform specimens were prepared by consolidating kaolin slurry under controlled loading conditions to achieve a defined stress history. A series of conventional single-stage and multistage consolidated undrained (CU) triaxial tests were conducted at different confining pressures. The results were analyzed using deviator stress–strain relationships, pore water pressure response, and effective stress paths. The comparison between testing methods indicates that multistage testing provides results comparable to conventional tests, with minor variations in stiffness and strength parameters due to progressive loading, densification, and accumulation of plastic strain. Additionally, strain-based interpretation shows that lower strain levels tend to overestimate apparent cohesion and underestimate friction angle, as full mobilization of shear resistance is not achieved.

Numerical simulations of selected triaxial tests were performed using PLAXIS with the Hardening Soil (HS) model. Model parameters were derived from laboratory data and refined through calibration to match the observed stress–strain response. The calibrated model successfully captured the nonlinear, stress-dependent stiffness behavior and the influence of confining pressure and stress history. Validation using independent kaolin data confirmed the robustness of the calibrated parameters, while comparison with published data on structured clays highlighted the limitations of the HS model in representing peak and post-peak softening behavior.

Furthermore, the modeling framework was applied to an independent clay dataset to evaluate its capability for parameter estimation using minimal experimental input. The results demonstrate that reasonable stress–strain behavior and representative strength parameters can be obtained from limited data through iterative calibration, although the accuracy depends on parameter selection and interpretation of experimental response.

Overall, the study demonstrates that slurry consolidation combined with multistage triaxial testing provides a reliable approach for characterizing soft clays, and that the Hardening Soil model, when properly calibrated, can effectively simulate their mechanical behavior. The findings contribute to improved understanding of testing methodologies and provide a practical framework for laboratory interpretation and numerical modeling of fine-grained soils.

Keywords

Multistage Triaxial Testing, Kaolin Clay, Slurry Reconstitution, Stress History, Overconsolidation, Hardening Soil Model, PLAXIS 2D, Stress-Dependent Stiffness, Undrained Shear Strength, Constitutive Modeling

Disciplines

Civil Engineering | Computational Engineering | Geotechnical Engineering

License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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Available for download on Tuesday, May 11, 2027

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