A micromechanics-based anisotropic friction–damage model for quasi-brittle rocks in monotonic compression considering dominant cracking process

In this work, a new micromechanics-based model is developed for describing the anisotropic mechanical behavior of quasi-brittle rocks in monotonic compression. The material is conceptualized as an isotropic elastic matrix embedded with randomly distributed initial microcracks. Based on experimental evidences and as an innovative approach, the stress-induced coupled anisotropic damage and plastic distortion are assumed related to the propagation and sliding of the dominant microcracks in the most unstable orientations under given loading state, instead of related to microcracks in all orientations as done in the previous studies. In this frame, by combining the thermodynamics framework and linear homogenization scheme, an energy-release-rate based damage law is developed for describing the induced anisotropic evolution of dominant microcracks. The plastic distortion is related to frictional sliding along the rough dominant microcracks and described by a damage-dependent friction law. The direction of dominant microcracks is identified by using Mohr maximization postulate. Further, the macroscopic failure strength is predicted from the coupled friction-damage analysis. The process for calibration of the microscopic parameters from macroscopic strength is developed. As another novelty of the present work, an enhanced semi-implicit return mapping (ESRM) algorithm is proposed to more efficiently dealing with two dissipation processes of plastic deformation and damage evolution. The effectiveness of the proposed model and the robustness of the ESRM algorithm are finally evaluated. • A new micromechanics-based anisotropic damage-fricton model is developed for quasi-brittle materials. • The concept of dominant microcracking process is introduced. • The specifc damage and fricton laws are proposed for the evoluton of dominant microcracks. • An enhanced semi-implicit return mapping (ESRM) algorithm is established through the use of decoupled plastc-damage correcton and sub-stepping scheme. • The performance and efciency of the proposed model and algorithm are fully demonstrated.