Finite-strain gradient-extended damage-plastic modeling of rock: Understanding catastrophe from material failure and structural instability

Rock, a natural geological material, exhibits diverse collapse modes that make predicting catastrophic behavior challenging. Material failure and structural instability each provide independent mechanical explanations for rock catastrophes. However, isolated perspectives often obscure the distinctions and connections between these two critical mechanisms. Here, we propose a finite-strain gradient-extended damage-plastic scheme within a thermodynamically consistent framework to encapsulate the indispensable dual effects of failure and instability. The crack propagation and frictional dissipation of crack clusters in rock materials inspire coupled damage-plastic theory, whereas the large displacement, large rotation and large strain of rock structures motivate the application of finite strain theory. The proposed scheme incorporates nonlocal gradient-enhanced terms to mitigate mesh dependence and is immune to spurious energy dissipation under cyclic loading. Constitutive treatment at finite strain retains the easily achievable features of the small deformation case. The model is validated through laboratory- and engineering-scale simulations, offering insights into the mechanisms of rock catastrophes. Our findings highlight the dual role of material failure and structural instability as interconnected drivers of rock catastrophes, offering a more holistic understanding for effective prediction and mitigation strategies.