An extended Cam Clay model for soft anisotropic rocks

The mechanical behaviour of soft sedimentary rocks in triaxial compression is modelled by means of a constitutive law which has been formulated by extending the original Cam Clay model. The geological material is assumed to be linearly elastic-plastic, strain-hardening, with fixed transverse isotropy. Theoretical predictions are compared to observed behaviour at different confining pressures of specimens of diatomite with various bedding inclinations. Although quantitative agreement is not always satisfactory, the trend of the tests is qualitatively well matched, what proves the paradigmatic value of this type of model not only for soils but even for soft rocks.