Multi-scale Simulation of Fracture Behavior of Underground Concrete Structures Based on Phase Field Theory

The appearance of cracks in underground concrete structures may lead to a decrease in various performance aspects, such as structural safety, applicability, and durability. From a numerical simulation perspective, it is crucial to carry out cracking and post-cracking mechanical behavior simulations of engineering structures. Among many numerical methods, the phase field model has significant advantages, with its primary feature being the need to refine the mesh in local areas to ensure the accuracy of the phase field simulation results. Based on the unified phase field theory, this paper proposes an adaptive multi-scale analysis method suitable for fracture analysis of underground concrete structures. Firstly, the problem domain is discretized using a coarse mesh, and phase field damage calculation is conducted to obtain an approximate crack damage zone area and derive the damage path. Subsequently, the geometric automatic encryption method is used to locally refine the elements on the damage path. An iterative calculation can be used to obtain a more accurate crack propagation path based on the finely refined local–global calculation mesh. The proposed method features a simple principle, convenient numerical implementation, and strong robustness. It can achieve accurate refinement and multi-scale analysis for complex underground concrete structures. Several typical underground concrete structure examples demonstrate and verify the feasibility and advantages of the proposed method.