Insights into natural tuff as a building material: Effects of natural joints on fracture fractal characteristics and energy evolution of rocks under impact load

•Analyzed the fractal characteristics and energy evolution of tuff fractures with different joint angles.•The damage modes and crack extension patterns of specimens with different joint angles were studied.•The crack evolution process of the specimen is reproduced by the finite discrete element method. Dynamic disturbances significantly affect the degradation of properties in rocks with natural joints. This study examines the impact of various joint angles on the fractal characteristics of fractures and energy evolution in tuff by conducting dynamic impact mechanical tests. Specimens were tested at joint angles ranging from 0° to 90° under constant strain rates. Analyses focused on the fractal dimensions of rock impact fractures, crack fractal dimensions, energy evolution, and numerical simulations to ascertain the influence of joint angles on the rock’s mechanical properties. Findings indicate that the failure mode of tuff specimens transitions from tensile to mixed tensile-shear failure and then back to tensile failure as joint angles change. Concurrently, the fractal dimension of breakage in tuff varied between 1.751 and 2.263, with corresponding crack fractal dimensions ranging from 0.999 to 1.478. Notably, both the dynamic compressive strength and energy dissipation of jointed tuff first decrease and then increase as the joint angle broadens, forming a “V” shaped distribution. Utilizing finite discrete element numerical calculations to replicate the crack expansion and evolution process, the study corroborates the significant influence of joint angle on the rock’s failure characteristics, which carries critical implications for rock engineering design.