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CASM: a unified state parameter model for clay and sand
Author(s) -
Yu H. S.
Publication year - 1998
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/(sici)1096-9853(199808)22:8<621::aid-nag937>3.0.co;2-8
Subject(s) - critical state soil mechanics , constitutive equation , geotechnical engineering , yield (engineering) , yield surface , stress space , plasticity , boundary value problem , mathematics , geology , engineering , physics , mathematical analysis , structural engineering , thermodynamics , finite element method
The purpose of this paper is to present a simple, unified critical state constitutive model for both clay and sand. The model, called CASM (Clay And Sand Model), is formulated in terms of the state parameter that is defined as the vertical distance between current state ( v , p ′) and the critical state line in v – ln p ′ space. The paper first shows that the standard Cam‐clay models (i.e. the original and modified Cam‐clay models) can be reformulated in terms of the state parameter. Although the standard Cam‐clay models prove to be successful in modelling normally consolidated clays, it is well known that they cannot predict many important features of the behavior of sands and overconsolidated clays. By adopting a general stress ratio‐state parameter relation to describe the state boundary surface of soils, it is shown that a simple, unified constitutive model (CASM) can be developed for both clay and sand. It is also demonstrated that the standard Cam‐clay yield surfaces can be either recovered or approximated as special cases of the yield locus assumed in CASM. The main feature of the proposed model is that a single set of yield and plastic potential functions has been used to model the behaviour of clay and sand under both drained and undrained loading conditions. In addition, it is shown that the behaviour of overconsolidated clays can also be satisfactorily modelled. Simplicity is a major advantage of the present state parameter model, as only two new material constants need to be introduced when compared with the standard Cam‐clay models. © 1998 John Wiley & Sons, Ltd.