New constitutive model based on disturbed state concept for shear deformation of rock joints

The mechanical behavior and constitutive relation of rock joints have caught more and more attention in the field of geotechnical engineering. The disturbed state concept (DSC) theory offers a powerful tool for building a constitutive model to interpret the mechanical response of geomaterials. In this paper, a new constitutive model for joint shear deformation was developed based on the DSC theory. The characteristics of quasi-elastic phase, pre-peak hardening phase, peak shear strength, post-peak softening phase and residual strength during the whole process of joint shear deformation are considered in this model. In the framework of this shear constitutive model, the rock material was assumed to consist of two kinds of micro-units with different mechanical responses, namely the relatively intact unit and the fully adjusted unit. Subsequently, the DSC theory was used to connect the mechanical behavior of micro-units with the macroscopic joint shear deformation characteristics, and a disturbance factor was introduced to reveal the disturbed state evolution process inside the rock. In addition, the proposed DSC model was simple in form, less in parameters and reasonable in physical meaning. The model was cross-validated by experimental data of different kinds of natural joints and artificial joint replicas. Finally, the model is compared with existing models, and the model effectiveness is quantitatively evaluated through statistical indicators. The values of R are greater than 0.9, and the AAREP and RMSE of the proposed DSC model are closer to 0 than those of other models. The research results can provide a valuable reference for further understanding of shear deformation mechanism.