Mechanical response and energy dissipation characteristics of bedded sandstone under uniaxial compression

Under uniaxial compression, the strength, deformation, and energy evolution characteristics of bedded sandstone depend not only on the inherent properties of the sandstone matrix but are also strongly controlled by factors such as bedding dip angles, bonding strength of bedding planes, and bedding density, exhibiting pronounced anisotropic behavior. At present, systematic studies on the mechanical properties and energy dissipation characteristics of bedded sandstone during uniaxial compression have mainly focused on a single bedding angle or a single energy parameter, lacking a synergistic analysis of energy parameters and mechanical parameters, as well as failure types and characteristics, under different bedding dip angles. To address this issue, bedded sandstone was taken as the research object, and uniaxial compression tests were conducted to systematically obtain stress-strain curves of bedded sandstone with five bedding dip angles of 0, 30, 45, 60, and 90°. The mechanical properties, including uniaxial compressive strength, elastic modulus, and Poisson's ratio, were analyzed, the dominant failure types and characteristics were observed, and the evolution laws of input energy, elastic energy, and dissipated energy were calculated based on the principle of energy conservation. The results showed that the bedding dip angle significantly influenced the mechanical properties of sandstone. The peak strength and elastic modulus exhibited a U-shaped variation with bedding dip angle, reaching the minimum at 45° and the maximum at 90°. Poisson's ratio showed a single-peak pattern, attaining the maximum value of 0.32 at 45°. The peak strain reached the maximum at 45° and the minimum at 90°. The failure types and characteristics evolved with bedding dip angle from through-bedding failure to along-bedding shear combined with local through-bedding failure, and finally to along-bedding shear slip. Specimens with bedding dip angles of 0° and 90° were dominated by through-bedding brittle failure, whereas those with 45° and 60° were dominated by along-bedding shear plastic failure. The input energy, elastic energy, and dissipated energy were all regulated by bedding dip angle. Specimens with bedding dip angles of 0° and 90° showed a higher proportion of elastic energy, which was released intensively at failure, while specimens with bedding dip angles of 30-60° exhibited a higher proportion of dissipated energy with a continuously increasing trend.