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Advances in Civil Engineering
Volume 2019, Article ID 6016350, 11 pages
Research Article

Enhancing Constitutive Models for Soils: Adding the Capability to Model Nonlinear Small Strain in Shear

Department of Civil Engineering, Aalto University, Espoo, Finland

Correspondence should be addressed to S. Seyedan; if.otlaa@nadeyes.davajdammahomdeyes

Received 30 June 2018; Accepted 30 January 2019; Published 28 April 2019

Academic Editor: Eric Lui

Copyright © 2019 S. Seyedan and W. T. Sołowski. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The deviatoric stress-deviatoric strain relationship in soils is highly nonlinear, especially in the small strain range. However, the constitutive models which aim to replicate the small strain nonlinearity are often complex and rarely used in geotechnical engineering practice. The goal of this study is to offer a simple way for updating the existing constitutive models, widely used in geotechnical practice, to take into account the small strain shear modulus changes. The study uses an existing small strain relationship to derive a yield surface. When the yield surface is introduced to an existing soil model, it enhances the model with the nonlinear deviatoric stress-deviatoric strain relationship in the small strain range. The paper also gives an example of such a model enhancement by combining the new yield surface with the Modified Cam Clay constitutive model. The validation simulations of the undrained triaxial tests on London Clay and Ham River sand with the upgraded constitutive models replicate the experiments clearly better than the base models, without any changes to existing model parameters and the core source code associated with the base model.