7.6.2 Parameters of the Modified Cam⁃clay model
The Modified Cam⁃clay model is based on five parameters：
（1）Poisson's ratio
Poissons ratio vur is a real elastic parameter and not a pseudo⁃elasticity constant as used in the Mohr⁃Coulomb model.Its value will usually be in the range between 0.1 and 0.2.
（2）Compression index and swelling index
These parameters can be obtained from an isotropic compression test including isotropic unloading.When plotting the natural logarithm of the mean stress as a function of the void ratio for clay⁃type materials，we can approximate the polt by two straight lines.The slope of the primary loading line gives the compression index and the slope of the unloading line gives the swelling index.These parameters can be obtained from a one⁃dimensional compression test.
（3）Tangent of the critical state line
In order to obtain the correct shear strength，the parameter M should be based on the friction angleφ.The critical state line is comparable with the Drucker⁃prager failure line，and represents a（circular）cone in principal stress space.Hence，the value of M can be obtained fromφ：
In addition to determining the shear strength，the parameter M has an important influence on the value of the coefficient of lateral earth pressure，K
in a state of normal consolidation.In general，when M is chosen such that the model predicts the correct shearing strength，the resulting value of K
is too high.
In addition to the output of standard stress and strain，the Modified Cam⁃clay model provides output（when being used）on state variables such as the isotropic pre⁃consolidation stress p，and the isotropic over⁃consolidation ration OCR.These parameters can be visualized by selecting the State parameters option from the Stresses menu.An overview of available state parameters is given below：
