Numerical Investigation of Bedding‐Plane Control Mechanisms on Blasting Fragmentation in Soft‐Hard Interbedded Rock Masses

Soft‐hard interbedded rock masses often exhibit heterogeneous blasting responses because bedding planes serve as both weak interfaces and wave‐impedance discontinuities. This study examines how bedding planes influence blast‐induced fragmentation and informs blasting design. LS‐DYNA simulations were performed for single‐hole blasting, presplit blasting, and production blasting under different charge positions, charge radii, and initiation sequences. The analysis focused on stress‐wave interaction, crack propagation, and explosion energy partitioning across soft and hard layers. The results indicate that the dominant mechanism is the bedding‐plane‐induced redistribution of dynamic stress and explosion energy. Under symmetric charging, early damage along the bedding plane unloads the hoop tensile stress near the interface, which suppresses crack propagation at small angles to the bedding plane; consequently, cracks preferentially extend normal to the bedding plane. Meanwhile, more explosion energy is absorbed by the soft rock, leading to stronger soft‐layer fragmentation than in the homogeneous case, whereas damage evolution in the hard rock is inhibited. Under asymmetric charging, charge placement in the hard rock facilitates cross‐layer energy transmission and rock mass fragmentation, whereas placement in the soft rock hinders this process. In presplit blasting, the spatial configuration of the bedding plane controls contour quality by modulating the inter‐hole tensile stress. For production blasting, hard‐rock‐first initiation with a short delay of 200–350 µs improves hard‐rock fragmentation and increases the fragmentation partitioning index E by 25%, whereas soft‐rock‐first initiation expands the blasted volume but keeps E below 0.5. The findings support bedding‐controlled optimization of blasting parameters.