Cam clay model

The two-evidenced plastic mechanisms are modelled by two yield surfaces combined within a cap model the modified Cam-Clay model is used for pore collapse whereas an internal friction model for friction failure (Collin el al. 2002b). Experimental results show that the chalk strength under extension can be overestimated using an internal friction model, a third yield surface is then adopted to limit traction stresses. 

Undrained strength ratio has been widely used as an empirical tool for soft soil. Wroth (1984) presented the interpretation of in situ soils within the general framework of the critical state soil mechanics and the deduced Cam clay model. He presented for engineering application the fundamental basis of the relationship ... 

The original Cam clay model employs isotropic hardening with strain hardening such as... 

Constitutive developments in the description of geomaterials have been the subject of extensive research over the past six decades. The scope of these developments is given by Desai and Siriwardane (1984), Darve (1990), Davis and Selvadurai (2002), and Pietruszczak (2010), etc. The Cam clay model (also known as the Cambridge model) is one that has been used widely to describe geomaterial behavior (Schofield and Wroth 1968 Parry 1971 Houlsby and Schofield 1993 Oka 1995). 

In this Section we present an outline of the Cam clay model. Note that we assume a conventional triaxial stress state ox = aj), and the following variables for stress and strain are introduced ... 

Finally we obtain the following yield function, which is referred to as the original Cam clay model. 

Since both the original and modified Cam clay models employ an associated flow rule, the plastic potential function g is the same as the yield function /. We use (6.88) and (6.98), and obtain the hardening coefficient h as follows ... 

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