Abstract: Taking red sandstone as the research object, the intact and flawed red sandstone specimens coated with liner were made using a cement-based thin spray-on liner. The study examined how the thin spray-on liner affected the strength, deformation, and energy evolution of intact and flawed red sandstone under uniaxial compression. Furthermore, the study analyzed how the thin spray-on liner influenced the crack propagation characteristics of sandstone with different inclination angles through particle flow PFC3D software. The results indicate that red sandstone coated with the thin spray-on liner exhibited higher peak strength and strain compared to uncoated specimens. Moreover, the improvement coefficient for flawed sandstone exceeded that of intact specimens. In the post-peak stage, the internal rock of specimens with the thin spray-on liner was damaged, resulting in the formation of tensile cracks on the liner’s surface, although the specimens did not fully collapse. The total energy, elastic energy, and dissipation energy of specimens with a thin spray-on liner are greater than those of uncoated specimens. Moreover, a greater amount of input total energy is converted into dissipation energy post-coating. The PFC3D simulation results indicate that applying a thin spray-on liner can increase the initiation stress and peak strength of crack specimens at different inclination angles. The influence of a thin spray-on liner on the failure modes of specimens with varying crack angles. Specifically, at a 15º inclination angle, the thin spray-on liner hinders the propagation of tensile cracks in the post-peak stage. Conversely, at a 75º inclination angle, the crack propagation behavior of specimens, whether coated or uncoated with a thin spray-on liner, is similar. These research findings can provide a reference for the application thin spray-on liners in engineering applications.

Key words: thin spray-on liner, flawed sandstone, strength characteristics, energy evolution, failure models, crack propagation