## 4 Discussions  
The present study systematically investigates the anisotropic creep behavior and failure mechanisms of coal under sustained loading, employing DIC-based full-field strain monitoring. The results demonstrate that bedding orientation plays a crucial role in governing the mechanical response, creep deformation, and ultimate failure mode of coal specimens. The bedding orientation has obvious influence on the creep properties of coal. The observed non-monotonic variation in peak strength--initially decreasing and then increasing with bedding angle--aligns with previous studies on anisotropic rocks (e.g., shale and layered coal). The minimum strength at intermediate angles (30-60\({}^{\circ}\)) suggests that bedding planes act as weak interfaces, facilitating shear slip under load. In contrast, at 0\({}^{\circ}\) and 90\({}^{\circ}\), the load is primarily resisted by the intact coal matrix, leading to higher strength. The creep behavior, characterized by distinct stages (instantaneous deformation, decelerating, steady-state, and accelerating creep), is consistent with classic rock creep theory. However, the pronounced creep deformation at high stress levels highlights the time-dependent weakening effect, which is critical for long-term stability assessment in coal mine roadways. The DIC analysis reveals that strain localization evolves differently depending on bedding orientation. For 0\({}^{\circ}\) and 90\({}^{\circ}\) specimens, strain concentrates along axial planes, culminating in tensile splitting fractures--a typical brittle failure mode under uniaxial compression. In contrast, 30\({}^{\circ}\) and 60\({}^{\circ}\) specimens exhibit strain accumulation along bedding planes, leading to combined tensile-shear failure. This transition from  
Figure 11: Evolution characteristics of horizontal spatial displacement along characteristic Measurement Line 2: (**a**–**d**) Bedding angles of 0\({}^{\circ}\), 30\({}^{\circ}\), 60\({}^{\circ}\), and 90\({}^{\circ}\), respectively.  
matrix-dominated to bedding-controlled failure underscores the importance of structural anisotropy in coal's mechanical behavior. Similar observations have been reported in layered rock mechanics, but the present study provides quantitative strain-field evidence, enhancing understanding of progressive damage evolution.  
The findings have direct implications for coal mine disaster prevention. The strong dependence of creep behavior on bedding angle suggests that roadway support strategies should account for local bedding orientation. For instance, in areas with intermediate bedding angles (30-60\({}^{\circ}\)), where shear failure dominates, enhanced reinforcement (e.g., bolting and grouting) along weak planes may be necessary. Additionally, the accelerating creep stage prior to failure could serve as a precursor for early warning systems, allowing for timely intervention. While this study provides valuable insights, certain limitations should be addressed in future research. The experiments were conducted under uniaxial conditions, whereas in situ coal is typically under triaxial stress. Future tests should incorporate confining pressure to better simulate underground conditions. A constitutive model incorporating bedding angle effects should be developed to predict coal's time-dependent deformation under various stress paths.