CASM: a unified state parameter model for clay and sand

Abstract

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.

Constitutive modelling of granular materials using a contact normal-based fabric tensor

“…In this situation, the relationship between e c and lnp c is better to be replaced by a bilinear relationship [5] or a nonlinear relationship [28]. As the effect of particle breakage is ignored in this work, we adopt the same linear relationship between e c and lnp c as that employed in the original CASM [89]. This relationship is valid until particle breakage occurs according to the results of laboratory tests [74,91], as shown in Fig.…”

“…The main aim of this paper is to present a critical state constitutive model for granular materials taking the fabric anisotropy into account. The model is developed on the basis of the isotropic bounding surface model named CASM_b [89,90]. A contact normal-based fabric tensor is additionally incorporated, and its evolution is formulated by using the hybrid evolution law proposed by the first author [21].…”

Constitutive modelling of fine‐grained gassy soil: A composite approach

“…This can cause extra volume contraction of the saturated matrix, which is similar to the effect of bubble flooding. For the three gassy clays used in this paper, such effect is small because of the extremely low solubility of typical types of biogas; (c) the effect of gas bubbles on yield surface shape (eg,) and dilatancy relationship should be considered to get better prediction of the effective stress paths in undrained triaxial compression.…”

Data Pruning of Tomographic Data for the Calibration of Strain Localization Models

“…The resin-bonded sand behavior is modeled with a relatively simple constitutive model based on the Cemented Clay and Sand Model (C-CASM). It consists in the extension of the Clay And Sand Model developed by Yu [39] for unbonded sand and clay to bonded geomaterials within the framework developed by Gens and Nova [40]. The C-CASM has been extensively described in [41].…”