The air-deck charge has been applied to the open-pit blasting for a long time. However, the effects of air-deck ratio on ground vibration are not clarified yet. In this study, the influences of air-deck ratios have been investigated based on field experiments. Firstly, five blasting tests with different air-deck ratios are conducted at an open pit mine. Their PPVs with different scaled distances have been collected and analyzed. The analysis results indicate that PPVs decrease exponentially with the increase of air-deck ratios at the same monitoring distances. Meanwhile, an improved PPV empirical predictor considering air-deck ratio is proposed. Through the massive vibration data collected from this open pit mine, it can be found that the improved empirical equation has the better prediction ability than the conventional equation.
Drill and blasting method has been widely applied to ore extraction and rock fragmentation in mining and civil industries (Nateghi 2012). During the rock explosion, the partial energies of explosives are released for rock fragmentation (Hagan 1979). The remains are delivered to surrounding environments and induce many adverse effects, such as ground vibrations, air shock waves, flying rocks and noises et al. Excessive vibrations often result in rock damages and structures instabilities (Verma et al. 2018). Hence, it has been concerned mostly by site operators among these negative effects (Yang et al. 2016). To effectively control vibration-related problems, many empirical predictors of ground vibrations have been developed and published (Mesec et al. 2010, Ak & Konuk 2008), among which peak particle velocity (PPV) is primarily used as the assessment indicator. The most popular PPV predictor is based on two parameters, maximum charge per delay and distance from blast site (Lu et al. 2017).
(equation 1)
where k and b are site specific constants which describe the characteristic of propagation media, blast design and geology. Qmax = the maximum charge per delay. α= 1/2 or 1/3, depending on the charge dimensions. When the ratio of the charge length to diameter is <6, the square root of weight is more appropriate.
