Study on dynamic mechanical properties and energy evolution law of cement jointed red sandstone under impact load

Natural joints of the rock mass are not closed. To investigate the influence of cement-jointed rock masses formed after grouting on engineering stability, this study conducted dynamic uniaxial compression tests on cement jointed red sandstone using the Hopkinson pressure bar device. The dynamic mechanical properties, failure modes, and energy dissipation characteristics of red sandstone with cemented joints with different dip angles were explored. The results indicate that the differences in stress-strain curves of jointed red sandstone are primarily reflected in the compaction stage, plastic stage, stress bimodal, and post-peak morphology at a 45° angle. Both the dynamic compressive strength and peak strain exhibit a U-shaped trend, initially decreasing and then increasing, reaching their minimum values at 45° joint inclination, while increasing with higher impact air pressure. The dynamic deformation modulus shows no significant variation but is closest to that of intact specimens at 90° inclination, where deformation resistance is the strongest. The energy reflection coefficient is an inverted U-shaped distribution, peaking at 45° inclination. The absorbed energy per unit volume also displays a U-shaped trend but is minimized at an inclination angle of 45°. The findings provide guidance and reference for blasting construction in jointed rock masses.