Dual-Threshold Charge Optimization for Cut Blasting Beneath a Surface Tank Farm

Cut blasting beneath operating tank farms poses a coupled design problem: the charge must create a cavity while keeping vibration contours outside protected structures. Existing checks evaluate peak particle velocity (PPV) at monitoring points or excavation quality separately, leaving the feasible charge range unclear. This study proposes a site-calibrated dual-threshold framework for a construction adit in a water-sealed cavern. A refined cut-hole damage model defines the lower charge threshold from damage connectivity, damage volume ratio and maximum block volume, while a field-scale vibration model defines the upper threshold from the 3.5 cm/s PPV contour relative to surface structures. Field fragmentation recognition and five vibration records support the comparison, with PPV errors of 0.24–3.37% and waveform correlations of r = 0.62–0.69. At the studied site, charges below 67.2 kg failed to satisfy cut-cavity criteria, whereas 79.8 and 84.0 kg caused the exceedance contour to contact or cross the structural boundary. A 75.6 kg grouped cut charge satisfied both thresholds and reduced cut explosive consumption by 10.0%. These charge values are site-specific; transfer to other excavations requires recalibration against local geology, structural layout and vibration limits. The framework converts charge selection into a bounded safety-and-effectiveness window for constrained underground excavations.