NorSand Implementation in Additive and Multiplicative Elastoplasticity
Loading...
Author(s)
Flournoy, Sean
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Problems characterized by large deformations are ubiquitous throughout the field of geotechnical engineering. From the cone penetration test to geohazards such as landslides, understanding soil behavior within the regime of large strains is essential for both effective design and risk mitigation with broad economic and humanitarian implications. The NorSand constitutive model, grounded in critical state soil mechanics, is a state parameter-based model capable of capturing realistic soil behavior of dilative and contractive sands. Modern implementations of NorSand typically assume small-strain kinematics, which become inaccurate when applied to problems involving substantial strains and rotations. In this thesis, we seek to enhance the predictive capabilities of NorSand, with a focus on model performance under large deformations. To this end, NorSand elastoplasticity is formulated according to both the additive decomposition of strain, which aligns with small strains, and the multiplicative decomposition of strain, which aligns with finite strains. Full descriptions of kinematics in the two regimes are given, with more rigorous mechanics emphasizing rotational invariance incorporated for the multiplicative formulation. A performance evaluation shows that both formulations agree with a benchmark model in the small- and medium-strain regime, with the multiplicative formulation capable of accurately describing soil response in the large-strain regime. Once verified, the multiplicative formulation of NorSand is implemented in Kratos Multiphysics, specifically its Geotechnical Particle Finite Element Method (G-PFEM) module, to simulate cone penetration. Cone penetration simulations give classical readings of tip resistance, sleeve friction, and excess pore pressures. Extension of NorSand into the finite strain regime represents an advancement in computational granular mechanics for large deformation problems.
Sponsor
Date
2025-04-23
Extent
Resource Type
Text
Resource Subtype
Thesis