Isolated boulders in roadways present substantial safety risks in mining operations. This research investigates the efficacy of blasting techniques for isolated boulder removal and their influence on adjacent rock damage, utilizing smooth blasting principles and the innovative S-ALE computational method. A precisely scaled 3D numerical model was developed based on a roadway project in a Yunnan underground metal mine to comprehensively examine how surrounding rock damage varies with different linear charge densities and borehole spacing configurations during smooth blasting of isolated boulders. The results indicate that: (1) surrounding rock damage follows an "inverse S-shaped" attenuation pattern with increasing distance from the blast center; (2) maximum damage depth demonstrates linear growth with higher linear charge density but shows fluctuating behavior with borehole spacing variations, peaking at 0.36 m and reaching minimum at 0.40 m spacing; (3) rock damage exhibits substantially greater sensitivity to linear change density adjustments compared to borehole spacing modifications. The optimal parameters balancing blasting efficiency and explosive consumption are determined to be a linear charge density of 0.30 kg/m (decoupling coefficient 1.43) and a borehole spacing of 0.40 m. The extensive free surface of isolated boulders results in a significantly shallower maximum damage depth than with conventional smooth blasting, consistent with observed reductions in plastic strain both perpendicular to and along the tunnel contour toward the free face. These results offer practical technical references for field applications.