A hypoplastic model for clays with stiffness anisotropy


The implemented model has been published by Mašín (2014). This model is an anisotropic version of the general clay hypoplasticity model described thoroughly in Mašín (2013). Structure of the anisotropic stiffness matrix described in Mašín and Rott (2014). Structured-soil specific model features are described in Mašín (2007). The model can be used with the intergranular strain concept, its original formulation is in Niemunis and Herle (1997), enhanced formulation implemented is described in Mašín (2013). Most of the cited journal papers available here for free download in the form of PDF preprints.


The original umat implementation has been developed by Claudio Tamagnini in 2005. It has since been further developed and updated to new models by David Mašín.


Description of the implementation and a user manual can be found here.



Mašín, D. (2014). Clay hypoplasticity model including stiffness anisotropy. Géotechnique 64, No. 3, 232-238. [Preprint PDF]

Mašín, D. (2013). Clay hypoplasticity with explicitly defined asymptotic states. Acta Geotechnica 8, No. 5, 481-496. [Preprint PDF]

Mašín, D. and Rott, J. (2014). Small strain stiffness anisotropy of natural sedimentary clays: review and a model. Acta Geotechnica 9, No. 2, 299-312. [Preprint PDF]

Mašín, D. (2007). A hypoplastic constitutive model for clays with meta-stable structure. Canadian Geotechnical Journal 44, No. 3, 363-375. [Preprint PDF]

Niemunis A and Herle I. (1997). Hypoplastic model for cohesionless soils with elastic strain range. Mechanics of Cohesive-Frictional Materials 2, 279-299.

©2017 David Mašín

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