An Assessment of the Post-peak Strain Behavior of Laboratory Intact Rock Specimens Based on Different Dilation Models

The complete stress-strain response of a number of intact rocks -including igneous, metamorphic and sedimentary ones- has been studied based on more than 300 compressive uniaxial and triaxial strength tests. Obtained results have been typically interpreted to register peak and residual strength as well as other post-peak parameters. Particular attention was given to the study of dilatancy. Dilation angle of these intact rocks was fitted to two pioneering but still recent dilatancy models (Alejano & Alonso 2005; Zhao & Cai 2010), having the feature of being plastic-shear-strain and confinement-stress dependent. The aim of this paper is to identify various dilation trends according to the type of rock tested and to check the ability of the models to accommodate actual results. This can be the base to further extend these models to the rock mass scale. To do that, the dilation angle database produced in our laboratory and some results from other tests taken from literature have been compiled in order to explain the main behavioral trends of this parameter according to the addressed models. These approaches are intended to insight rock behavior models emphasizing the post-failure stage as well as to contribute to more realistic but still practical dilatancy models.