A Heuristic Elastoplastic Damage Constitutive Modeling Method for Geomaterials: From Strength Criterion to Analytical Full-Spectrum Stress–Strain Curves

This paper presents an elastoplastic damage constitutive modeling method in the thermodynamic framework for geomaterials. The model within this method starts from a strength criterion and shall well describe the full-spectrum stress–strain curves (i.e., curves of Classes I and II). First, a yield function is constructed in the stress space, on the basis of the strength criterion. A heuristic continuous and smooth unified hardening or softening parameter is then introduced into the yield function, which ensures that the yield function has the same form as the strength criterion at the peak stress state. Finally, an appropriate damage criterion is developed to consider the development of microcrack-induced damage. Unlike existing elastoplastic damage models, the yield function in stress space is not related to the damage. In this case, the model established using this modeling method shall derive some analytical solutions under several loading paths, which could be used to calibrate the model parameters and to validate the accuracy of the numerical algorithm. For application, the proposed method is utilized to construct an elastoplastic damage model based on the generalized Hoek–Brown strength criterion. The analytical stress–strain relations of the proposed model are used to predict the mechanical behavior of several types of rock. Comparisons between model predictions and experimental data show that this model can well describe the mechanical behavior of the investigated materials, including strength nonlinearity, strain hardening or softening, volume dilation, and brittle–ductile transition.