Study on Pillar Stability and Control Strategies Incorporating Blasting-induced Damage Effects During Stope Excavation

Given the substantial explosive volumes and charges involved in underground room-and-pillar mining operations, blasting-induced damage to retained pillars becomes severe, compromising structural integrity and potentially triggering catastrophic failures. This study established a mathematical correlation between necessary pillar safety width and height while accounting for blasting damage effects, revealing how conventional designs that neglect such damage may dangerously overestimate both pillar dimensions and load-bearing capacity. A 20 m×80 m×80 m pillar structure from a representative mining area was taken as a case study. Utilizing parameters derived from laboratory uniaxial compression and Brazilian splitting tests, an ANSYS/LS-DYNA model of fan-pattern long-hole blasting was developed to analyze pillar damage and vibration characteristics under simultaneous initiation versus millisecond-delay initiation(25 ms and 50 ms). Findings reveal that simultaneous initiation causes stress wave superposition, resulting in unilateral damaged depths of 4~5 m, while delayed initiation reduces damage to approximately 3~3.5 m(25 ms delay) and about 2 m(50 ms delay). Additionally, a practical implementation scheme is proposed that combines a 50 ms interval delay with an optimized detonation sequence. This approach prioritizes creating localized free surfaces to direct energy dissipation toward excavated voids, reducing average surrounding rock damage depth to 1~1.5 m while decreasing pillar surface peak vibrations by approximately 16.6%. These findings provide practical guidance for pillar-width design and blasting damage control in room-and-pillar mining operations.