• Single-hole dispersed charge creates a cavity and a new free surface, enhancing deep-hole blasting impact over stress wave superposition alone.
• Dual-hole continuous-charge detonation is challenging, whereas short-delay detonation effectively exploits stress wave superposition and prolongs explosive gas action.
• The cavities formed by dispersed charges can be strategically used to improve the efficiency of dual-hole composite charge blasting.
• Numerical models validated by engineering experiments demonstrate that optimized delay times significantly improve blasting outcomes in single free-face rock masses.