Numerical Study of Asymmetry in Blast Pressure Propagation and Rock Damage Under Eccentric Decoupled Charges

The eccentric decoupled charge (EDC) is widely used in blasting engineering, but the combined effects of decoupling ratio, coupling medium, and explosive position (eccentricity coefficient) on blast pressure propagation and rock damage remain insufficiently understood. In this study, the RHT material model in LS-DYNA is calibrated using fracture patterns from laboratory tests, and a series of cubic single-hole numerical models is established to examine the influence of charging parameters on pressure evolution and rock damage. The results show that EDC blasting generates a clear eccentricity effect in pressure propagation: the coupled side exhibits a higher peak pressure and faster loading, while the decoupled side experiences delayed wave arrival and lower peak pressure. This asymmetry intensifies with increasing decoupling ratio and eccentricity coefficient. Pressure decay follows a nonlinear power function, with attenuation in the axial direction being greater than in the radial direction. The total damage volume decreases with increasing decoupling ratio, but the eccentricity of the damage pattern becomes more evident, especially in the crushed zone. Different coupling media influence this effect: air/sand coupling readily produces eccentricity effects, while water coupling requires a larger decoupling ratio to do so. From an energy perspective, the evolving asymmetry in fracture behavior is closely linked to the redistribution of internal energy between the coupled and decoupled sides, as governed by the charging configuration.