The time-dependent deformation behavior of silty mudstone brings pronounced difficulties for the construction and maintenance of slope engineering, which has attracted much attention. This study examines the creep characteristics of silty mudstone through multistaged loading tests and studies the creep-induced microstructural evolution using Scanning Electron Microscopy (SEM). To mitigate the variability caused by natural defects in the rock, similar material specimens were prepared to substitute silty mudstone for experiments. The results demonstrate that creep strain escalates stepwise with stress level, with the magnitude of each increment being contingent upon the applied confining pressure ( $\sigma _{3}$ ). The strain rate undergoes three phases including attenuation, stabilization, and acceleration. Cumulative strain correlates positively with $\sigma _{3}$ , while the initial creep rate declines before slightly increasing. Creep failure predominantly manifests in a shear pattern, with $\sigma _{3}$ controlling the development of fractures in terms of their length, number, and angle. SEM analysis reveals that increased $\sigma _{3}$ facilitates the expansion of transgranular cracks, displaying a coupled ductile–brittle fracture mode. Furthermore, $\sigma _{3}$ variably affects the micropore morphology (pore size, area, roughness, and regularity), with the differences in pore structures under various $\sigma _{3}$ being distinguished by the fractal dimension. Also, the fractal dimension is positively correlated with porosity, which can be quantitatively characterized using a nonlinear logarithmic function. The interaction between particles and cement, coupled with the development of cracks and pores, is identified as the primary mechanism of structural failure during the creep process.
