Abstract
The deck-charge structure, also referred to as axially decoupled charge structure, has found widespread application in open-pit rock excavation to enhance blasting performance. However, the relationships between blast-induced fragmentation and deck-charge structures remain unclear. This paper aims to experimentally investigate the influences of deck ratio, deck position and deck material on blast-induced fragmentation. Small-scale single-hole blasting experiments were conducted on concrete blocks (400×400×200 mm3). The dynamic evolution process of model fracturing under blast loading was captured using a high-speed camera. The displacement and strain fields were analyzed employing a 3D digital image correlation system (DIC), and the fragment size distribution (FSD) was determined through ImageJ, which is an advanced image-processing code. Meanwhile, the blasthole wall pressure (BWP) was monitored through the embedded gauges in the test block. The experimental results indicate that under a deck charge blasting, the host concrete experiences three phases, i.e., crushing phase, further crushing and fracturing phase, and radial crack developing phase. The fragmentation performance increases within a reasonable range of air-deck ratio, while an excessive deck ratio results in worse fragmentation compared to fully coupled charge blasting. The center deck charge yields the superior fragmentation, followed by the double-ends deck charge and top deck charge. Water-deck charge produces finer fragmentation than air-deck and PE-deck charges. EPS-deck charge is not conducive to fragmentation, but it may provide a solution for reducing vibration and controlling damage to the remaining rock mass. Based on the experiment results, production blasts with fully coupled charge, center air-deck charge and center water-deck charge were conducted in an open-pit mine, revealing that the proposed center deck charge blasting results in at least a 15% reduction in median fragment size, with center water-deck charge outperforming in rock fragmentation due to its ability to maximize the utilization of explosive energy for rock fracturing.